Resist resin

ABSTRACT

According to the present invention, a resist resin having in its structure a specific bridged-bond-containing aliphatic ring, and a resist composition comprising the same are provided. By using this resist composition, a resist pattern excellent in both transparency against short-wavelength light and dry-etching resistance can be formed by alkali development with high resolution.

FIELD OF THE INVENTION

The present invention relates to resins useful for resists, and toresist compositions comprising the same. The present invention alsorelates to a pattern forming process and a process for producingsemiconductors using the resist compositions.

BACKGROUND OF THE INVENTION

In manufacturing processes of electronic components such as LSIs, finepatterning techniques utilizing photolithography have conventionallybeen adopted. Namely, a resist solution is firstly coated onto thesurface of a substrate or the like to form a resist film; and the resistfilm is subjected to pattern-wise exposure to light, and then totreatments such as development by an alkaline developer to form a resistpattern. Subsequently, the bare surface of the substrate or the like isdry-etched by utilizing this resist pattern as an anti-etching mask toform minute lines and openings, and the remaining resist is finallyremoved by means of ashing.

Therefore, the resist herein used is generally required to have highdry-etching resistance. From this point of view, resists containingaromatic compounds have widely been used. Specifically, there have beendeveloped a large number of resists containing, as base resins, novolakresins that are alkali-soluble.

On the other hand, in line with the trend toward high-density,high-integration LSIs and the like, the above-described fine patterningtechniques have been improved in recent years so that patterning can beattained at the level of sub-half micron order; and this tendency towardfine patterning is expected to be more remarkable. Indeed, thewavelengths of light sources for use in photolithography are being madeshorter; and it is now attempted to form fine resist patterns by usingArF excimer laser light (wavelength 193 nm), or a 5-fold higher harmonicwave of a YAG laser (wavelength 218 nm).

However, the resists containing, as base resins, resins containingaromatic compounds, which have commonly been used heretofore, have sucha peculiarity that benzene nucleus contained in the compounds show highlight absorption against the above-described short-wavelength light.Therefore, when it is tried to form a resist pattern, it is difficult toallow light to fully reach the substrate side of a resist film when thefilm is exposed to light. It has thus been difficult to form, with highsensitivity and high accuracy, patterns excellent in shape.

Under such circumstances, there is a strong demand for the developmentof highly transparent resist resins suitable also for photolithographywhich uses ArF excimer laser light, or a 5-fold higher harmonic wave ofa YAG laser.

From this viewpoint, those resists containing alicyclic compounds inplace of aromatic compounds are now attracting attention. JapanesePatent Laid-Open Patent Publication No. 39665/1992, for instance,describes the following example: alkali-solubility is imparted to aresist which is excellent in both dry-etching resistance andtransparency against short-wavelength light and which comprises acompound containing adamantane that is a bridged-bond-containingalicyclic compound, by copolymerizing the resist and another acryliccompound; and a resist pattern is formed by alkali development, by theuse of this alkali-solubility-imparted resist.

As shown in Japanese Patent Laid-Open Publication No. 199467/1995, thereis known a resist material containing, as tricyclodecanyl structure, analicyclic compound having 5-membered rings, which is one ofbridged-bond-containing alicyclic compounds.

However, in the case where a resist pattern is formed by means of alkalidevelopment by the use of a resist containing such an alicycliccompound, various problems will be brought about. This is because thealicyclic structure such as adamantane skeleton has extremely highhydrophobicity, so that the difference in alkali-solubility between thisalicyclic structure and a group which imparts alkali solubility to theresist is great.

For example, the predetermined area of the resist film cannot beuniformly dissolved and removed by development, so that the lowering ofresolution is brought about. Moreover, the lowering of resolution isalso caused due to the swelling of the resist pattern that occurs afterdevelopment, and the resist film is cracked or undergoes surfaceroughening because even the area of the resist film that is supposed toremain after development is partly dissolved. Further, the separation ofthe resist pattern is often caused due to the penetration of an alkalinesolution into the resist film-substrate interface. Furthermore, phaseseparation between the part having the alicyclic structure and the groupwhich imparts alkali solubility, such as carboxylic acid moiety, tendsto proceed in the polymer, so that it is difficult to obtain ahomogeneous resist solution. In addition, such a resist solution showspoor coating performance.

In order to reduce the hydrophobicity of these alicyclic compounds, theintroduction of a polar group such as COOH or OH group into thealicyclic compounds has been proposed (Japanese Patent Laid-OpenPublications No. 83076/1998, No. 252324/1995 and No. 221519/1997). Ithas been confirmed that the solubility is considerably improved in allof these compounds.

However, the structure of these alicyclic compounds is such that COOH orOH group is combined with secondary or primary carbon atom of thealiphatic ring, so that this COOH or OH group tends to secondarily reactwith other substituents in the resists. Moreover, these compounds havelow glass transition temperatures, so that they tend to bring about thelowering of resolution, and the swelling of the pattern afterdevelopment.

An object of the present invention is therefore to provide, byovercoming the aforementioned problems, a resist resin which can be acomponent of a resist composition having high transparency againstshort-wavelength light and high dry-etching resistance, capable offorming a resist pattern excellent in adhesion and resolution by meansof alkali development.

Another object of the present invention is to provide theabove-described resist composition.

A further object of the present invention is to provide a patternforming process using the resist composition.

SUMMARY OF THE INVENTION

Resist resin I according to the present invention is obtained byhomopolymerizing at least one monomer selected from monomers representedby the following general formulas (I-1) and (I-2):

wherein R is acryloyl or methacryloyl group, R₁₁ and R₁₂ independentlyrepresent hydrogen atom or a monovalent alkyl group, and R₁₃ is OHgroup, ═O group, COOH group or COOR₁₄ group (R₁₄ is a monovalent organicgroup), or by copolymerizing the monomer(s) and any other vinyl monomer.

Resist resin II according to the present invention comprises abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring.

Resist resin III according to the present invention comprises abridged-bond-containing aliphatic ring, at least one carbon constitutingthe bridged-bond-containing aliphatic ring being combined with oxygenthrough double bond.

A resist composition according to the present invention comprises one ofthe above resist resins I, II and III, and a photo acid generator.

A pattern forming process according to the present invention comprisesthe steps of:

-   -   coating a resist composition comprising one of the        above-described resist resins onto a substrate,    -   subjecting the resist composition coated onto the substrate to        pattern-wise exposure, and    -   developing the resist composition exposed to light.

Further, a process for producing a semiconductor device according to thepresent invention comprises the steps of:

-   -   coating the above-described resist composition onto a substrate,    -   subjecting the resist composition coated onto the substrate to        pattern-wise exposure,    -   developing the resist composition exposed to light, thereby        forming a patterned photomask, and    -   etching an etching film by dry etching, using the photomask as a        mask.

DESCRIPTION OF DRAWINGS

In the drawings,

FIGS. 1 to 3 are cross-sectional views showing processes for producingsemiconductor devices, using resist compositions of the presentinvention; and

FIGS. 4 and 5 are ¹H-NMR charts of Compounds (III-E) and (III-F),respectively, for use in the production of resist resins of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a resist resin obtainable byhomopolymerizing at least one monomer selected from monomers representedby the following general formulas (I-1) and (I-2):

or by copolymerizing the monomer(s) and any other vinyl monomer.

The present invention also relates to a resist resin having abridged-bond-containing aliphatic ring, at least two oxygen-containingpolar groups being combined with a tertiary carbon atom of thebridged-bond-containing aliphatic ring.

Further, the present invention relates to a resist resin comprising apolymer or condensate of a monomer having a bridged-bond-containingaliphatic ring composed of at least two rings selected from the groupconsisting of 5-membered rings, 6-membered rings and 7-membered rings,at least two oxygen-containing polar groups being combined with atertiary carbon atom of the bridged-bond-containing aliphatic ring.

Furthermore, the present invention relates to a resist compositioncomprising the above-described resist resin, and a photo acid generator.

Furthermore, the present invention relates to a pattern forming processcomprising the steps of coating the above-described resist compositiononto a substrate, subjecting the resist composition coated onto thesubstrate to pattern-wise exposure, and developing the resistcomposition exposed to light.

By the use of the resist resin, resist composition, and pattern formingprocess according to the present invention, it is possible to form, bymeans of alkali development, a resist pattern excellent in transparencyagainst short-wavelength light, dry-etching resistance, and resolution.

A resist composition according to the present invention comprises asmain components a resist resin and a photo acid generator. Thesecomponents will be explained in detail hereinafter.

<Resist Resins>

Resist resins according to the present invention will be describedhereinafter.

[Resist Resin I]

In one aspect of the present invention, resist resin I is obtained byhomopolymerizing at least one monomer selected from monomers representedby the following general formulas (I-1) and (I-2):

wherein R is acryloyl or methacryloyl group, R₁₁ and R₁₂ independentlyrepresent hydrogen atom or a monovalent alkyl group, and R₁₃ is OHgroup, ═O group, COOH group or COOR₁₄ group (R₁₄ is a monovalent organicgroup), or by copolymerizing the monomer(s) and any other vinyl monomer.

In the monomers represented by the general formulas (I-1) and (I-2), R₁₁and R₁₂ are hydrogen atom or a monovalent alkyl group. Since thesegroups are released and decomposed more sensitively in the presence ofan acid, the resist resin becomes alkali-soluble. It is preferable thatR₁₁ and R₁₂ be not hydrogen atom at the same time, but methyl, ethyl,propyl or isopropyl group because the latter groups are released anddecomposed more sensitively than hydrogen atom.

R₁₃ is OH group, ═O group, COOH group, or COOR₁₄ group (R₁₄ is amonovalent organic group). Since the resist resin contains R₁₃, it showsreduced hydrophobicity. By introducing this group, it has becomepossible to improve the adhesion between a photosensitive resistcomposition and a substrate, and the alkali-solubility of a polymer. Inorder to enhance this function, a plurality of R₁₃s may be introduced.In particular, ═O group is preferred because it hardly causesundesirable reaction with other groups introduced as side chains. It ispreferable that OH group, COOH group or COOR₁₄ group (R₁₄ is amonovalent organic group) introduced as R₁₃ is combined with a tertiarycarbon atom as will be described in [Resist Resin II]. Further, althoughR is acryloyl or methacryloyl group, acryloyl or methacryloyl groupsubstituted with cyano group or halogen atom is also included in thescope of the present invention.

In the case where a copolymer of a monomer represented by the generalformula (I-1) or (I-2) and another vinyl monomer is used, the content ofthe monomer represented by the general formula (I-1) or (I-2) ispreferably from 10 to 90 mol %, more preferably from 30 to 70 mol % ofthe copolymer. When this monomer content is less than 10 mol %, theremay not fully be obtained such a function that the unexposed area of theresist resin remains closely adhered to a substrate and keepsdry-etching resistance high, while the exposed area of the resist resinreleases the alicyclic structure to increase the alkali-solubility ofthe polymer. In contrast, when the monomer content exceeds 90 mol %, itbecomes difficult to control the alkali-solubility of the polymer, sothat the production cost tends to increase.

The vinyl monomer that is copolymerized with a monomer represented bythe general formula (I-1) or (I-2) is preferably at least one monomerselected from monomers represented by the following general formulas(I-3), (I-4), (I-5), (I-6) and (I-7):

wherein R₃₁ represents hydrogen atom, or at least one group selectedfrom the group consisting of OH group, OR₁₄ group (R₁₄ is a monovalentorganic group) and ═O group, R₃₂ represents hydrogen atom or amonovalent organic group, and R₄₁ represents vinyl, acryloyl ormethacryloyl group.

When any of these monomers is copolymerized with a monomer representedby the general formula (I-1), a copolymer having improvedalkali-solubility and dry-etching resistance can be obtained. Such acopolymer can therefore impart further improved functions to a resistcomposition. In particular, when a monomer represented by the generalformula (I-7) is used, the resulting copolymer shows improveddry-etching resistance, so that the use of this monomer is morepreferred. Further, a monomer represented by the formula (I-2) is morepreferable than a monomer represented by the formula (I-1); a monomerrepresented by the formula (I-4) is more preferable than a monomerrepresented by the formula (I-3); and a monomer represented by theformula (I-6) is more preferable than a monomer represented by theformula (I-5). This is because monomers represented by the formulas(I-2), (I-4) and (I-6) have higher carbon contents than thoserepresented by the formulas (I-1), (I-3) and (I-5), respectively, sothat the former monomers are more excellent than the latter monomers inresistance to ordinary energy gases such as CF₄.

Further, vinyl monomers other than monomers represented by the abovegeneral formulas (I-3), (I-4), (I-5), (I-6) and (I-7) may also be used.In this case, it is desirable that the vinyl monomers havebridged-bond-containing alicyclic structure. The bridged-bond-containingalicyclic structure includes cyclic cyclo or bicyclo compoundsrepresented by the general formula C_(n)H_(2n) (n is an integer of 3 ormore), and condensed rings thereof. Specific examples of this structureinclude cyclobutane ring, cyclopentane ring, cyclohexane ring,cycloheptane ring, cross-linked-hydrocarbon-introduced cyclobutane,cyclopentane, cyclohexane and cyclopentane rings, spiro rings such asspiroheptane and spirooctane, terpene rings such as norbonyl ring,adamantyl ring, bornene ring, menthyl ring and menthane ring, steroidalskeletons such as thujane, sabinene, thujone, carane, carene, pinane,norpinane, bornane, fenchane, tricyclene and cholesteric rings, bileacid, digitaloides, camphor ring, isocamphor ring, sesquiterpene ring,santone ring, diterpene ring, triterpene ring, and steroid saponins.

Further, it has been known that, since the wavelengths of absorptionbands are shifted not only by alicyclic structure but also condensedpolycyclic structure, the transparency at 193 nm can be ensured even bycondensed polycyclic structure (T. ushirogouchi et al., Proc. SPIE, Vol.2195 (1994), page 205, etc.). Therefore, the object of the presentinvention can be attained even by vinyl monomers having condensedpolycyclic structure.

Examples of vinyl monomers having condensed polycyclic structure are asfollows: indene, indane, benzofulvene, 1-indanone, 2-indanone,1,3-indandione, ninhydrin, naphthalene, methylnaphthalene,ethylnaphthalene, dimethylnaphthalene, cadalene, vinylnaphthalene,1,2-dihydronaphthalene, 1,4-dihydronaphthalene,1,2,3,4-tetrahydronaphthalene tetralene,1,2,3,4,5,6,7,8-octahydronaphthalene, cis-decalene, trans-decalene,fluoronaphthalene, chloronaphthalene, bromonaphthalene, iodonaphthalene,dichloronaphthalene, (chloromethyl)naphthalene, 1-naphthol, 2-naphthol,naphthalene diol, 1,2,3,4-tetrahydro-1-naphthol,1,2,3,4-tetrahydro-2-naphthol, 5,6,7,8-tetrahydro-1-naphthol,5,6,7,8-tetrahydro-2-naphthol, decahydro-1-naphthol,decahydro-2-naphthol, chloronaphthol, nitronaphthol, aminonaphthol,methoxynaphthalene, ethoxynaphthalene, naphthyl ether, naphthyl acetate,naphthoaldehyde, naphthalene dicarbaldehyde, hydroxynaphthoaldehyde,dinaphthyl ketone, 1(2H)-nephthalene, alpha-tetralone, beta-tetralone,alpha-decalone, beta-decalone, 1,2-naphthoquinone, 1,4-naphthoquinone,2,6-naphthoquinone, 2-methyl-1,4-naphthoquinone,5-hydroxy-1,4-naphthoquinone, isonaphthazaline, naphthoeic acid,1-naphthol-4-carboxylic acid, naphthalic acid, naphthalic anhydride,1-naphthylacetic acid, thionaphthol, N,N-dimethylnaphthylamine,naphthonitrile, nitronaphthalene, pentalene, azulene, heptalene,fluorene, 9-phenylfluorene, nitrofluorene, 9-fluorenol, fluorenone,anthracene, methylanthracene, dimethylanthracene,9,10-dihydroanthracene, anthrol, anthranol, hydroanthranol,dihyroxyanthracene, anthragallol, 1(4H)-anthracenone, anthrone,anthrarobin, chrysarobin, oxanthrone, anthracenecarboxylic acid,anthramine, nitroanthracene, anthracenequinone, anthraquinone,methylanthraquinone, hydroxyanthraquinone, phenanthrene, phenanthrol,phenanthrenehydroquinone, phenanthraquinone, biphenylene, s-indacene,as-indacene, phenarene, teracene, chrysene, 5,6-chrysoquinone, pyrene,1,6-pyrenequinone, triphenylene, benzo[alpha]anthracene,benzo[alpha]anthracene-7,12-quinone, benzanthrone, aceanthrene,acephenanthrylene, acephenanthrene, 17H-cyclopeneta[alpha]-phenanthrene,fluoranthene, pleiadene, pentacene, pentaphen, picene, pirylene, dibenzo[a,j]anthracene, benzo[alpha]pyrene, coronene, pyranthrene, andpyranthrone.

The resist resin according to the present invention can be obtained bypolymerizing, by means of radical, cationic or anionic polymerization, apolymerizable compound having, in its molecule, alicyclic structure intowhich an acidic substituent has been introduced, and polymerizabledouble bond. In general, a monomer having polymerizable double bond likeone in an alicylic group contained in polymer backbone can produce ahigh-molecular-weight polymer when it is subjected to cationic oranionic polymerization. However, in the present invention, even if themolecular weight of the resist resin is low, there is no problem as longas a film can be formed by the use of the resin. Therefore, thepolymerization may be conducted by a simple technique such as radicalpolymerization, and the resulting polymer that is a mixture oflow-molecular-weight compounds and high-molecular-weight compounds mayalso be used as the resist resin.

At this time, the polymerizable compound may also be copolymerized withacrylic acid, maleic anhydride, an ester substitution product of acrylicacid or maleic anhydride, vinyl phenol, vinyl naphthol, hydroxyethylmethacrylate, SO₂, or the like.

Further, it is also possible to control the alkali-solubility of thepolymer, and to improve the adhesion between the resist and a substrateby copolymerizing the polymerizable compound and an alkali-solublecompound whose alkali-soluble group has been protected by a groupdecomposable by an acid, having dissolution-preventing ability. However,when the transparency of the resist against short-wavelength light istaken into consideration, it is preferable to copolymerize thepolymerizable compound and a compound having no molecular skeleton whoselight absorption in short-wavelength ranges is great, such as benzenenucleus. Specifically, it is desirable that the absorbance of thepolymer against light having a wavelength of 193 nm be 4 or less,preferably 2 or less per 1 micrometer. In the case where the resistcomposition of the present invention is used as an upper resist to becoated onto a substrate having an intermediate layer, the aboveabsorbance may be made as high as approximately 8 per 1 micrometer.

It is preferable to make the average molecular weight of the resistresin according to the present invention in the range of 1,000 to500,000, more preferably in the range of 3,000 to 50,000. A resist resinhaving an average molecular weight of less than 1,000 is unfavorable forforming a resist film having sufficiently high mechanical strength. Onthe contrary, when the average molecular weight of the resist resin ismade higher than 500,000, it becomes difficult to form a resist patternexcellent in resolution. These compounds are, in general, mixtures ofthe compound of the present invention and other copolymers havingvarious molecular weights.

The resist resin according to the present invention shows its effectseven when it has a relatively low molecular weight; and even if theaverage molecular weights of the components of the resin are localizedin the range of, for example, 500 to 1,000, the resist resin isprevented from being dissolved unevenly. Therefore, such a resin is alsodesirable one. Moreover, in this case, even if the monomers areremaining in the resin in a large amount, the dissolution properties anddry-etching resistance of the resin are hardly marred.

[Resist Resin II]

Resist resin II according to the present invention comprises, in itsmain or side chain, a bridged-bond-containing aliphatic ring, at leasttwo oxygen-containing polar groups being combined with a tertiary carbonatom of the bridged-bond-containing aliphatic ring.

In the resist resin II according to the present invention, at least twooxygen-containing polar groups are combined with a tertiary carbon atomof the above-described bridged-bond-containing aliphatic ring. Whenthree or more oxygen-containing polar groups are combined with atertiary carbon atom of the above-described bridged-bond-containingaliphatic ring, these groups can highly contribute to the improvement inadhesion between the resin and a substrate, and in the alkali-solubilityof the resin. Therefore, such a resin is more preferred.

The oxygen-containing polar groups combined with onebridged-bond-containing aliphatic ring may be the same or different.

In the present invention, the oxygen-containing polar group is asubstituent having carbon-oxygen bond, a difference in electronegativitybetween carbon and oxygen being great. Examples of such a group includesubstituted or unsubstituted carboxyl groups, substituted orunsubstituted cyclic lactone groups, substituted or unsubstitutedhydroxyl groups, aldehyde group, groups containing peroxides,substituted or unsubstituted urethane groups, acyl groups, and carbonategroups.

When the oxygen-containing polar groups are combined with a tertiarycarbon atom of the bridged-bond-containing aliphatic ring through—(CH₂)n- (n is a natural number), these polar groups have high degree offreedom of movement. Therefore, there cannot be obtained the effectsequal to those obtainable when the oxygen-containing polar groups arecombined directly with a tertiary carbon atom of thebridged-bond-containing aliphatic ring. For this reason, such a case isexcluded from the state of “oxygen-containing polar groups combined witha tertiary carbon atom”.

In view of the properties of the resist composition, it is particularlydesirable when polarity is taken into consideration that theoxygen-containing polar group be at least one organic group selectedfrom substituted or unsubstituted carboxyl groups, substituted orunsubstituted hydroxyl groups, and substituents containing cycliclactones. By the use of these groups, the effects of improving adhesionand solubility can be obtained.

Further, such an oxygen-containing polar group is preferred that thesubstituent introduced to the carboxyl group be a cyclic lactone. It isalso preferable that the carboxyl group form an acid anhydride togetherwith another bridged-bond-containing alicyclic compound having acarboxylic acid. This is because a compound having such anoxygen-containing polar group shows particularly increased solubility.

Furthermore, the bridged-bond-containing aliphatic ring may contain notonly two or more oxygen-containing polar groups at a tertiary carbonatom of the ring, but also a non-reactive polar group such as ketone orlactone introduced to the secondary or primary carbon atom of the ring.

The resist resin II reveals its effects through the following action.

The above-described oxygen-containing polar group is restricted in itsmovement around carbon as compared with the conventional case where thepolar group is combined with carbon at the secondary or primay carbonatom. For instance, in the case of a resin having abridged-bond-containing aliphatic ring in which hydroxyl group isintroduced to the carbon atom, the hydroxyl group has freedom ofmovement only in the direction around the carbon, and the molecularmotion of the hydroxyl group is thus small. In contrast, when hydroxylgroup is introduced to carbon at the secondary or primary carbon atom ofthe ring, it has freedom of movement not only in the direction aroundthe carbon but also in the direction parallel to the carbon. Themolecular motion of such hydroxyl group is thus great.

For this reason, when a resin having a bridged-bond-containing aliphaticring, oxygen-containing polar groups being introduced to tertiary carbonatom of the bridged-bond-containing aliphatic ring is used as the baseresin of a resist composition, the free volume is decreased, so that theresist composition has a high glass transition temperature (Tg). As aresult, high resolution can be obtained.

In fact, when a resin having such a structure that OH group has beenintroduced to carbon at the 2-position of a bridged-bond-containingaliphatic ring is compared with a resin having such a structure that OHgroup has been introduced to tertiary carbon atom of abridged-bond-containing aliphatic ring, the latter is found to have a Tgabout 10 to 20° C. higher than that of the former. Moreover, a resin inwhich OH group has been introduced to an alicyclic skeleton throughmethylene, like conventionally known hydroxymethyl tricyclodecanylacrylate compounds, has a Tg 10 to 20° C. lower than the above-describedresin having OH group at the secondary carbon atom of thebridged-bond-containing aliphatic ring. Therefore, the differencebetween this resin and the resin having OH group at the 3-position ofthe bridged-bond-containing aliphatic ring becomes more evident.

In addition, since the molecular motion of OH group introduced totertiary carbon atom of the ring is small as mentioned previously, adeveloper hardly penetrates the unexposed area. Therefore, the patternscarcely swells.

Moreover, the resin according to the present invention should have twoor more oxygen-containing polar groups introduced to tertiary carbonatom of a bridged-bond-containing aliphatic ring. These groups play animportant role in improvement in adhesion to a substrate andalkali-solubility which are the essential properties of resists. Sincethese groups are combined with tertiary carbon atom, they have freedomof movement only in the direction around the carbon, and cannot turnlaterally. It is therefore highly probable that these groups turn tooutside in terms of the backbone. For this reason, the resin has highercompatibility with an alkaline solvent that is brought into contact withthe resin, and higher adhesion to a substrate.

Oxygen-containing polar groups, especially OH group and COOH group,combined with carbon at the secondary or primary carbon atom show highreactivity, so that they tend to cause secondary cross-linking reactionby heating. In particular, chemically amplified positive resists havesuch a crucial problem that pattern formation cannot be attained whilethey are processed by heating. This tendency can be more remarkable whenthe resin has acid anhydride structure.

However, oxygen-containing polar groups combined with tertiary carbonatom as in the present invention show low reactivity, and hardly causesecondary cross-linking reaction when heated. Therefore, theaforementioned problem is not brought about in this case.

Thus, according to the present invention, it is possible to form, byalkali development, a resist pattern excellent in transparency againstshort-wavelength light, dry-etching resistance, adhesion and resolution.

In the resist resin II according to the present invention, thepercentage of the bridged-bond-containing alicyclic ring is desirablyfrom 20 to 90% by weight of the resin. When this percentage is notwithin this range, the resist resin has reduced dry-etching resistanceor alkali-solubility.

In the resin according to the present invention, it is desirable that atleast one of the above-described oxygen-containing polar groups be COOHgroup protected by a dissolution-preventive group (a soluble group whichcan be decomposed by an acid). If the resin has such a group, the resistlayer shows alkali-solubility after it has caused deprotection reactionby an acid. Further, the rate of dissolution of the unexposed area isreduced due to the existence of the protective group, so that highdissolution contrast can be attained. In addition, since the resin hashydrophilicity, the alkali-solubility of the resin is also maintainedproperly.

In particular, a resin obtained by copolymerizing hydroxyadamantylacrylate having hydroxyl group combined with tertiary carbon atom andtetrahydropyranyl acrylate can be mentioned as an example of the resinhaving the above-described protective group. This resin has, in itsunexposed area, no alkali-soluble group but has hydroxyl groupprotruding from its polymer chain; the resin thus shows increasedhydrophilicity. Therefore, the unexposed area of the resist film willnever be unevenly dissolved. In addition, the resist film showsincreased adhesion to a substrate.

Furthermore, it is desirable that the resin in the present inventioncontains acid anhydride structure in its structure, that is, in its mainor side chain, and that at least one of the above-describedoxygen-containing polar groups is hydroxyl group. Namely, in the casewhere the resin contains, in its structure, both OH group that is notinvolved in linkage, and acid anhydride structure, a secondaryself-crosslinking reaction is suppressed. Therefore, the effects of thepolar groups combined with tertiary carbon atom become remarkable, andthe resin shows high contrast. Such a resin is thus desirable as apositive resist.

The resin according to the present invention can be obtained bypolymerizing or condensing starting monomers in one of the followingcombinations i) to iv), by any of various means such as radicalpolymerization or living polymerization:

-   -   i) a combination of one or more monomers comprising a        bridged-bond-containing aliphatic ring, at least two        oxygen-containing polar groups being combined with tertiary        carbon atom of the bridged-bond-containing aliphatic ring        (structure A);    -   ii) a combination of one or more monomers having the structure        A, and one or more monomers comprising a bridged-bond-containing        aliphatic ring, least two oxygen-containing polar groups being        combined with secondary or primay carbon atom of the        bridged-bond-containing aliphatic ring (structure B);    -   iii) a combination of one or more monomers having the structure        A, and one or more monomers having structure (structure C) that        is neither the structure A nor the structure B; and    -   iv) a combination of one or more monomers having the structure        A, one or more monomers having the structure B, and one or more        monomers having the structure C.

The bridged-bond-containing aliphatic ring and oxygen-containing polargroups contained in the structure A or B can include thepreviously-mentioned bridged-bond-containing aliphatic rings andoxygen-containing polar groups, respectively.

In the case where the resin according to the present invention isobtained by using monomers in the above combination (i) or (ii), it isdesirable that the oxygen-containing polar groups combined with thebridged-bond-containing aliphatic ring contained in the resin becombined with tertiary carbon atom as many as possible. It is sufficientthat at least 70%, more preferably 90% or more of the oxygen-containingpolar groups combined with the bridged-bond-containing aliphatic ringare combined with tertiary carbon atom of the ring. There may be such acase that a monomer having the structure A is to contain a monomerhaving oxygen-containing polar groups combined with carbon at the2-position due to the side reaction caused when the former monomer issynthesized, inevitably becoming equal to the above combination (ii).Such a case is also permissible.

When the resin according to the present invention is obtained by usingmonomers in the combination of (iii) or (iv), the effects of the monomerin which oxygen-containing polar groups are introduced to tertiarycarbon atom can be observed when the monomer having the structure Aexceeds at least 15%, more preferably 20% or more of the total molaramount of the monomers constituting the resin, although this percentagemay vary depending upon the copolymerization ratio of the monomer havingthe structure A to the other monomers.

A monomer useful as the starting monomer in the present invention,having a bridged-bond-containing aliphatic ring, at least twooxygen-containing polar groups being combined with tertiary carbon atomof the bridged-bond-containing aliphatic ring (structure A) can beobtained by oxidizing an alicyclic compound, and extracting the desiredcomponent. Alternatively, the above monomer can conveniently be obtainedby partly hydrolyzing an alicyclic compound by bromination, or by meansof air oxidation using a catalyst (Japanese Patent Laid-Open PublicationNo. 35522/1999). Further, it is also possible to use acrylated ormethacrylated compounds obtained by further subjecting theabove-obtained compounds to addition reaction using a catalyst, or toesterification to be carried out by an acid chloride process.

In the case where the resin of the present invention is obtained bypolymerization, it is desirable to use a monomer having the structure A,and, as a monomer having another structure, an acrylic or vinylcompound. It is particularly preferable to use, as the monomer, anacrylic compound to obtain an acrylic or methacrylic resin because it isreadily polymerizable. An acrylic or methacrylic resin can be obtainedby polymerizing, as the monomer having the structure A, a monomer whosebridged-bond-containing aliphatic ring contains, as theoxygen-containing polar groups, at least one acryloyloxy ormethacryloyloxy group. The acryloyloxy or methacryloyloxy group may besubstituted with cyano group or halogen atom.

In particular, when the resin of the present invention is obtained bypolymerizing, as the monomer having the structure A, a compoundrepresented by the following general formula (II-1) or (II-2), it showsexcellent dry-etching resistance, solubility and adhesion, and has ahigh glass transition temperature; such a resin is thus desirable.

wherein R₁ represents acryloyl or methacryloyl group, R₂ representshydrogen atom or an oxygen-containing polar group, and R₃ representshydrogen atom, a group decomposable by an acid, a cyclic substituenthaving a lactone, or a substituent having acid anhydride structureformed with a bridged-bond-containing alicyclic compound containing acarboxylic acid.

Examples of the group for R₃, decomposable by an acid include tert-butylgroup, tetrahydropyranyl group and acetal group. Further, in order toobtain high contrast between exposed and unexposed areas, it isdesirable that R₃can also act as a dissolution-preventive group.

wherein R₁ represents acryloyl or methacryloyl group, R₂ representshydrogen atom or an oxygen-containing polar group, and R₄ representshydroxyl group, a cyclic substituent having a lactone, or a substituenthaving acid anhydride structure formed with a bridged-bond-containingalicyclic compound containing a carboxylic acid.

In the case where the resin of the present invention is obtained bycondensation, the resin is desirably an alicyclic-backbone-type polymeror oligomer obtainable by dehydration condensation, using, as themonomer having the structure A, a monomer having abridged-bond-containing aliphatic ring in which two or more organicgroups of at least one of carboxyl group and hydroxyl group are combinedwith tertiary carbon atom, or a monomer further having lactone structureat tertiary carbon atom.

In the above-described polymer or oligomer, the monomer is combined withthe backbone of the polymer through linkage decomposable by an acid.Examples of this linkage include ester linkage and acid anhydridelinkage. In this case, the resin is of alicyclic backbone type, and haspolyester or polyacid anhydride structure.

When the resin has the polyester or polyacid anhydride structure ofalicyclic backbone type, the resist composition undergoes, before andafter exposure, drastic decomposition of the molecular skeletonincluding the backbone of the resin, and high resolution can thus beobtained. Moreover, the number of free secondary oxygen-containing polargroups is small in this resin, so that dehydration condensation sidereaction is scarcely caused and that the resin has a high Tg. Such aresin is therefore desirable. Further, since the resin hasbridged-bond-containing alicyclic structure, the solubility of theexposed area of the resist is remarkably improved with the coatingperformance and adhesion of the resist maintained high. Moreover, thedissolution contrast between exposed area and unexposed area can beimproved. In addition, since the resist has bridged-bond-containingalicyclic structure in its backbone, it can also show sufficiently highdry-etching resistance.

In particular, when the resin according to the present invention has apolyester or polyacid anhydride linkage that is formed by dehydrationcondensation between carboxyl group and hydroxyl group, and/or betweencarboxyl groups, the resin is excellent in the property of beingdecomposed by an acid, has high stability and high transparency, and canreadily be synthesized. This resin is thus desirable.

The above-described ester linkage is obtained by the dehydrationcondensation of a polyvalent carboxylic acid with an alicyclicpolyvalent alcoholic compound, using a catalyst; or by the desalting ofa polyvalent carboxylic acid chloride with a polyvalent alcoholiccompound. Alternatively, the ester linkage may be obtained by thedehydration condensation of one or more compounds containing a pluralityof carboxyl groups and alcohol groups.

The above-described acid anhydride linkage is obtained by thedehydration condensation of one or more polyvalent carboxylic acidcompounds.

The resin may contain several types of linkage (e.g., ester linkage andacid anhydride linkage) at the same time when the linkage of differenttypes is formed by the same type of reaction, especially by dehydrationcondensation reaction.

In general, polymers or oligomers containing acid anhydride linkage havesuch an advantage that they are excellent in alkali-solubility. It isgenerally considered that these acid anhydride compounds are readilyhydrolizable and unstable. However, acid anhydride linkage that isinterposed between bulky alicyclic compounds as in the present inventionis extremely stable, and imparts alkali-solubility suitable for patternformation. On the other hand, polymers or oligomers having ester linkageare stable in any solvent, and show a great change in dissolution rateas the decomposition of an acid catalyst proceeds, so that they have theadvantage of improving the resolution. By using these different types oflinkage in combination, the solubility and resolution that are morepreferable for resists can be obtained at the same time. In this case,it is sufficient that the ratio of acid anhydride linkage to esterlinkage is from 1:20 to 5:1; and, more preferably, the acid anhydridelinkage content is 10% or more and less than 50%.

Further, a resin containing acid anhydride structure in its structure,that is, in the main or side chain, wherein at least one of theabove-described oxygen-containing polar groups is hydroxyl group isdesirable as the resin of the present invention as mentioned previously.

Such a resin may be obtained by polymerizing or condensing, in thepreviously mentioned manner, a monomer having the structure A in whichat least one of the oxygen-containing polar groups is hydroxyl group.For instance, not only poly(ester-acid anhydride) compounds but alsocopolymers comprising alicyclic structure having OH group at its3-position, and maleic anhydride can be mentioned.

On the other hand, examples of compounds having the structure C includethe following: tert-butyl acrylate, tert-butyl methacrylate, methacrylicacid, acrylic acid, alpha-chloroacrylic acid and esters thereof,trifluoromethyl acrylate, alpha-methylstyrene, trimethylsilylmethacrylate, trimethylsilyl alpha-chloroacrylate, trimethylsilylmethylalpha-chloroacrylate, maleic anhydride, tetrahydropyranyl methacrylate,tetrahydropyranyl alpha-chloroacrylate, methyl methacrylate, t-butylalpha-chloroacrylate, butadiene, glycidyl methacrylate, isobornylmethacrylate, menthyl methacrylate, norbornyl methacrylate, adamantylmethacrylate, cycloolefin compounds, acrylates having lactone skeletonin acrylic side chains, and acrylates having epoxy skeleton. Of these,tetrahydropyranyl methacrylate and maleic anhydride are particularlypreferable for improving the resolution because they do not causesecondary reaction that is commonly caused. Further, in order to improvethe dry-etching resistance of a resin, cycloolefin compounds areconveniently used as comonomers; and in order to improve thedevelopability, acrylic compounds having lactone skeleton in the sidechains thereof are conveniently used as comonomers.

In the case where the resin according to the present invention is anarylic or methacrylic resin, the weight-average molecular weight (Mw) ofthe resin, calculated in terms of polystyrene, is preferably from 2,000to 100,000, more preferably from 5,000 to 60,000 although it may varydepending upon the desired properties of the resist composition. Whenthe Mw is less than 2,000, the resin tends to have poor film-formingproperties. On the other hand, when the Mw is in excess of 100,000, theresin tends to have decreased developability and resolution. Further,the molecular-weight distribution Mw/Mn is preferably from 1 to 5, morepreferably from 1 to 2.

Further, in the case where the resin according to the present inventionis a polyester or polyacid anhydride condensate of alicyclic backbonetype, it is preferable to adjust the average molecular weight of theresin, calculated in terms of polystyrene to 100-30,000. A resin havingan average molecular weight of less than 100 is unfavorable for forminga resist film excellent in mechanical strength, heat resistance, andcoating performance. On the other hand, when the average molecularweight of the polymer compound is in excess of 30,000, the compound hasimpaired alkali-solubility, so that it becomes difficult to form aresist pattern with high resolution. These compounds are generallymixtures of components having various molecular weights.

The resin of the present invention reveals its effects even when it hasrelatively low molecular weight like a dimer; and, even such a resinthat the average molecular weights of its components are localized, forexample, to the range of 100 to 1,000 is also effective. Further, inthis case, even if less than 10% of the monomers is remaining in thecopolymer, the copolymer scarcely undergoes deterioration of dissolutionproperties or dry-etching resistance.

[Resist Resin III]

Resist resin III that is the base of a resist composition of the presentinvention comprises a bridged-bond-containing aliphatic ring in itsstructure.

The bridged-bond-containing aliphatic ring is a combination of at leasttwo aliphatic rings selected from 5-membered rings, 6-membered rings and7-membered rings. The aliphatic rings may be either the same ordifferent in terms of the number of members constituting one ring. Inaddition, the bridged-bond-containing alicyclic skeleton may contain, inaddition to carbon, such elements as oxygen, sulfur and nitrogen.

The above bridged-bond-containing aliphatic ring can include thosealiphatic rings enumerated in the item of [Resist Resin I].

The resist resin III according to the present invention contains theabove-described bridged-bond-containing aliphatic ring in its structure,at least one of the carbons constituting the bridged-bond-containingaliphatic ring being combined with oxygen through double bond to form>C═O.

It is desirable that the resin according to the present invention beincorporated into a resist composition so that the amount of >C═O willbe 40% by weight or more of the solid matter of the resist composition.When this amount is less than 40% by weight, it is difficult to obtain,by alkali development, a resist pattern excellent in both resolution andadhesion. Moreover, the resulting resist pattern may have impaireddry-etching resistance.

Further, the resin according to the present invention may be a resinhaving the above-described bridged-bond-containing alicyclic skeleton inits structure, at least one of the rings constituting thebridged-bond-containing alicylic skeleton being a lactone ring; that is,a resin containing —C(═O)—O— in one ring.

A resin having such bridged-bond-containing alicyclic skeletoncontaining a lactone ring is to have further improved alkali-solubility,dry-etching resistance and adhesion.

When the bridged-bond-containing alicyclic skeleton in the resin is alactone ring, the resin can show hydrophilicity higher than that of aresin to which a substituent containing OH, sulfonyl or nitro group hasbeen introduced as mentioned in PRIOR ART. Moreover, since such a resinis not so reactive as a resin having a substituent containing OH group,side reaction by which a resist is made negative hardly occurs.

In this case, it is preferable that the components are so incorporatedthat the amount of lactonyl group will be 30 mol % or more of the resin.When this amount is less than 30 mol %, it is difficult to form, byalkali development, a resist pattern excellent in both resolution andadhesion. Moreover, the resulting resist pattern tends to have decreasedadhesion.

The resin of the present invention can be made in the following manner(a) or (b). (a) Some of the carbons contained in an alicyclic compoundhaving the above-described bridged-bond-containing aliphatic ring areoxidized by the use of a strong oxidizing agent. By this, methylenecarbon contained in the bridged-bond-containing aliphatic ring isoxidized, and an alicyclic compound (alicyclic compound (A)) having thebridged-bond-containing aliphatic ring into which >O═O has beenintroduced can be obtained.

By further allowing the oxidizing agent to act on this compound to causeoxidation, —O— is introduced into the ring. Thus, there can be obtainedan alicyclic compound (alicyclic compound (B)) having thebridged-bond-containing aliphatic ring whose bridged-bond-containingalicyclic structure has been made into a lactone ring.

A resin according to the present invention can then be obtained byhomopolymerizing, as a monomer, the above alicylcic compound (A) or (B),or a derivative thereof obtained by introducing, into the alicycliccompound (A) or (B), a group that can act as a binding member during thepolymerization step to be conducted later, or by copolymerizing such amonomer and any other monomer.

-   -   (b) A resin according to the present invention can be obtained        by allowing a strong oxidizing agent to react with some of the        carbons constituting a resin having the above-described        bridged-bond-containing alicyclic skeleton to oxidize the        carbons.

Specifically, the following [1] or [2] can be mentioned as thepolymerization method described in the above (a).

-   -   [1] The alicyclic compound (A) or (B) which is a monomer useful        for synthesizing a resin according to the present invention, or,        as its derivative, a compound having polymerizable double bond        is polymerized by means of radical, anionic, or cationic        polymerization, or polymerization using a Ziegler-Natta        catalyst. In general, a monomer having polymerizable double        bond, such as one having alicyclic moiety in its main chain, can        yield a polymer having a higher molecular weight when it is        polymerized by the use of a Ziegler-Natta catalyst. However, the        resin according to the present invention brings about no problem        as long as it 15 can form a film even if the molecular weight of        the resin is low. Therefore, the monomer may be polymerized by a        simple technique such as radical polymerization, and the        resulting mixture of low-molecular-weight compounds and        high-molecular-weight compounds may be used.

Examples of the above-described compound having polymerizable doublebond include compounds obtained by oxidizing norbornyl di(mono)ene,tricyclodeca (mono)diene or tetracyclodeca (mono)diene to introduce >C═Oor —C(═O)—O— into at least one of the aliphatic rings.

Further, it is preferable that the above-described compound containingpolymerizable double bond be an alcohol or an ester compound of acarboxylic acid. This is because such a compound is readilypolymerizable.

Furthermore, it is desirable that the above-described compound havingpolymerizable double bond be an acrylic or methacrylic ester compound.This is because such a compound has high polymerizability and can bepolymerized at any composition ratio. It is more preferable thatadamantane, tricyclodecane, tetracyclodecane or hydronaphthaleneskeleton be contained in the side chain of the acrylic or methacrylicester compound.

It is particularly desirable to obtain a resin of the present inventionby polymerizing, as a monomer, a compound represented by the followinggeneral formula (III-1a) or (III-1b) because the resulting resin isexcellent in dry-etching resistance and adhesion:

wherein R represents acryloyl or methacryloyl group.

In the compound represented by the general formula (1), carbonyl groupmay be introduced to the 2-position.

Further, it is desirable to obtain a resin of the present invention bypolymerizing, as a monomer, a compound represented by the followinggeneral formula (III-2a) or (III-2b) because these compounds have highpolymerizability and can be polymerized at any composition ratio:

wherein R represents acryloyl or methacryloyl group, and R₁ and R₂represent an alkyl group or a group decomposable by an acid. R₁ and R₂may be partly cross-linked to form a cyclic compound. Moreover,adamantylidene group may be introduced to the 2-position.

Furthermore, it is desirable to obtain a resin of the present inventionby polymerizing, as a monomer, a compound represented by the followinggeneral formula (III-3a), (III-3b), or (III-3c) because the resultingresin is excellent in dry-etching resistance and adhesion:

wherein R represents acryloyl or methacryloyl group. The hydrogen atomsof compound (III-3a), (III-3b) and (III-3c) are able to be substitutedby other substituent.

Furthermore, it is desirable to obtain a resin of the present inventionby polymerizing, as a monomer, a compound represented by the followinggeneral formula (III-4) because this compound is highly polymerizableand can be polymerized at any composition ratio:

wherein R₁ represents acryloyl or methacryloyl group.

-   -   [2] At least either one of a polyester resin or a polyacid        anhydride resin is obtained by homopolymerizing the alicyclic        compound (A) or (B) that is a monomer useful for synthesizing a        resin according to the present invention, or, as its derivative,        a compound containing two or more organic groups of at least one        of hydroxyl group and carboxyl group. Alternatively, the above        compound and another compound containing two or more groups of        at least one of hydroxyl group and carboxyl group may be        subjected to condensation polymerization to obtain a desired        resin.    -   (2]-1: A polyester resin can be obtained by the dehydration        condensation of the alicyclic compound (A) or (B) that is a        monomer useful for synthesizing a resin according to the present        invention, or, as its derivative, a compound having        monohydroxy-monocarboxylic acid skeleton. Alternatively, a        polyester resin may be obtained by the dehydration condensation        of the alicyclic compound (A) or (B) that is a monomer useful        for synthesizing a resin according to the present invention, or,        as its derivative, a polyvalent carboxylic acid compound        containing two or more groups of at least one of hydroxyl group        and carboxyl group with a polyvalent alcoholic compound.        Further, a polyester resin may also be obtained by the reaction        between the alicyclic compound (A) or (B) that is useful for        synthesizing a resin according to the present invention, or a        derivative of the alicyclic compound that is a polyvalent        alcohol having two or more groups of at least one of hydroxyl        group and carboxyl group and conjugated polycyclic condensed        aromatic skeleton, and a polyvalent carboxylic acid. The above        polyvalent carboxylic acid or polyvalent alcohol may be a        mixture of two or more compounds.

A polyester resin can also be obtained not only by the above-describedprocesses but also by any of widely-used processes for synthesizingpolyesters, for instance, by carrying out the ring-opening reaction of alactone, the polymerization of a polyvalent carboxylic acid and apolyvalent alcohol by the ring-opening reaction of an acid anhydride, orthe polymerization of a polyvalent carboxylic acid and a polyvalentepoxy compound in the case where a polyvalent carboxylic acid chlorideand a polyvalent alcohol are subjected to desalting reaction by the useof triethylamine or the like as a catalyst.

-   -   [2]-2: A polyacid anhydride resin can be obtained by the use of        the alicyclic compound (A) or (B) that is useful for        synthesizing a resin according to the present invention, or its        derivative that is a polyvalent carboxylic acid having two or        more groups of at least one of hydroxyl group and carboxyl        group; this monomer is singly subjected to dehydration        condensation. Alternatively, a polyacid anhydride resin can be        obtained by using the alicyclic compound (A) or (B), or a        derivative thereof that is a polyvalent carboxylic acid having        two or more groups of at least one of hydroxyl group and        carboxyl group, and a polyvalent carboxylic acid chloride; these        monomers are subjected to desalting reaction by using        triethylamine or like as a catalyst.

It is noted that the resin according to the present invention maycontain both polyester linkage and polyacid anhydride linkage at thesame time.

It is desirable to carry out dehydration condensation between a part ofor all of >C═O contained in the resin of the present invention, and acompound having active methylene. By doing so, it is possible to furtherimpart, to the resin, adhesion and the property of being decomposed byan acid.

The above-described compound having active methylene herein denotes, forinstance, those compounds having electron-attracting substituents onboth sides of methylene. Examples of electron-attracting groups includecarbonyl group, carboxyl group, esters of carbonyl or carboxyl groups,sulfonyl group, sulfonate group, cyano group, and halogen atoms. Ofthese, malonic acid derivatives represented by the following generalformula (5) are desirable from the viewpoints of adhesion, resolutionand developability:R₃O(CO)CH₂(CO)OR₄   (5)wherein R₃ and R₄, which may be the same or different, represent analkyl group, or a group that can be decomposed by an acid. Further, R₃and R₄ may be partly combined with each other to form a cyclic compound.In particular, when R₃ and R₄ are tert-butyl group, or when the compoundhaving active methylene is a meldrum compound, the property of beingdecomposed by an acid, and solubility are improved, respectively.

In the present invention, it is preferable to incorporate the componentsso that the amount of the alicyclic structure into which double bondformed by condensation with active methylene has been introduced will be10% by weight or more of the solid matter of the resist. When thisamount is less than 10% by weight, it is difficult to form, by alkalidevelopment, a resist pattern excellent in both resolution and adhesion.In addition, the resulting resist pattern tends to have impaireddry-etching resistance. On the other hand, when the above amount is mademore than 90%, the transparency is lowered.

It is preferable to make the average molecular weight of the resinaccording to the present invention, calculated in terms of polystyrene,from 500 to 500,000. A resin having an average molecular weight of lessthan 500 is unfavorable for forming a resist film having sufficientlyhigh mechanical strength. On the contrary, when the average molecularweight of the polymer compound is in excess of 500,000, it is difficultto form a resist pattern excellent in resolution. The resin component ofa resist composition is, in general, a mixture consisting of componentshaving different molecular weights. The resin according to the presentinvention reveals its effects even when it has a low molecular weight.For example, even a resin containing components having average molecularweights of 500 to 1,000 is prevented from being dissolved unevenly, sothat such a resin is also desirable. Moreover, in this case, even ifmany monomers are remaining in the resin, it is acceptable as long asthe resin can form a film without causing any problem.

[Structure Common to Resist Resins I, II and III]

A resin according to the present invention can be obtained bycopolymerizing the monomer and any of various vinyl compounds. Examplesof useful vinyl compounds include methyl acrylate, methyl methacrylate,alpha-chloroacrylate, cyanoacrylate, trifluoromethyl acrylate,alpha-methylstyrene, trimethylsilyl methacrylate, trimethylsilylalpha-chloroacrylate, trimethylsilylmethyl alpha-chloroacrylate, maleicanhydride, tetrahydropyranyl methacrylate, tetrahydropyranylalpha-chloroacrylate, t-butyl methacrylate, t-butylalpha-chloroacrylate, butadiene, glycidyl methacrylate, isobornylmethacryate, menthyl methacrylate, norbornyl methacrylate, adamantylmethacrylate and allyl methacrylate.

Moreover, when the control of the alkali-solubility of the resin and theimprovement in adhesion between the resist and a substrate are takeninto consideration, it is preferable to copolymerize the monomer andacrylic acid, maleic anhydride, an ester substitution product of acrylicacid or maleic anhydride, or an ankali-soluble compound such as vinylphenol, vinyl naphthol, naphthol oxymethacrylate or SO₂. It is alsopossible to copolymerize the monomer with a compound obtained byprotecting the alkali-soluble group of any of the above alkali-solublecompounds by a dissolution-preventive group (a group decomposable by anacid) having the ability of preventing dissolution.

It is preferable to introduce a dissolution-preventive group (a solublegroup decomposable by an acid) into the molecule of a resin according tothe present invention because the resulting resin has improvedresolution. A dissolution-preventive group can be introduced into aresin by using a monomer compound having the dissolution-preventivegroup when the resin is synthesized.

A cyclic tertiary ester group having a lactone, or a substituent havingacid anhydride structure formed with a bridged-bond-containing alicycliccompound having a carboxylic acid acts as a soluble group decomposableby an acid. Therefore, such a group can conveniently be used as thedissolution-preventive group.

Examples of dissolution-preventive groups include the following: esterssuch as t-butyl ester, isopropyl ester, ethyl ester, methyl ester andbenzyl ester; ethers such as tetrahydropyranyl ether; alkoxy carbonatessuch as t-butoxy carbonate, methoxy carbonate and ethoxy carbonate;silyl ethers such as trimethylsilyl ether, triethylsilyl ether andtriphenylsilyl ether; esters such as isopropyl ester, tetrahydropyranylester, tetrahydrofuranyl ester, methoxyethoxy methyl ester,2-trimethylsilylethoxymethyl ester, 3-oxocyclohexyl ester, isobornylester, trimethylsilyl ester, triethylsilyl ester, isopropyldimethylsilylester, di-t-butylmethylsilyl ester, oxazole, 2-alkyl-1,3-oxazoline,4-alkyl-5-oxo-1,3-oxazoline and 5-alkyl-4-oxy-1,3-dioxolane; ethers suchas t-butoxycarbonyl ether, t-butoxy-methyl ether, 4-pentenyloxymethylether, tetrahydropyranyl ether, tetrahydro-thiopyranyl ether,3-bromotetrahydropyranyl ether, 1-methoxycyclohexyl ether,4-methoxytetrahydropyranyl ether, 4-methoxytetrahydrothiopyranyl ether,1,4-dioxane-2-yl ether, tetrahydrofuranyl ether, tetrahydrothiofuranylether,2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ylether, t-butyl ether, trimethylsilyl ether, triethylsilyl ether,triisopropylsilyl ether, dimethylisopropylsilyl ether,diethylisopropylsilyl ether, dimethylsesquisilyl ether andt-butyldimethylsilyl ether; acetals such as methylene acetal, ethylideneacetal and 2,2,2-trichloroethylidene acetal; ketals such as1-t-butylethylidene ketal, isopropylidene ketal (acetonide),cyclopentylidene ketal, cyclohexylidene ketal and cycloheptylideneketal; cyclic orthoesters such as methoxymethylene acetal,ethoxymethylene acetal, dimethoxymethylene orthoester,1-methoxyethylidene orthoester, 1-ethoxyethylidene orthoester,1,2-dimethoxyethylidene orthoester, 1-N,N-dimethylaminoethylideneorthoester and 2-oxacyclopentylidene orthoester; silyl ketene acetalssuch as trimethylsilylsilyl ketene acetal, triethylsilyl ketene acetaland t-butyldimethylsilyl ketene acetal; silyl ethers such asdi-t-butylsilyl ether, 1,3-1′, 1′, 3′, 3′-tetraisopropyldisiloxanylideneether and tetra-t-butoxy-disiloxane-1,3-diylidene ether; acyclic acetalsand ketals such as dimethyl acetal, dimethyl ketal,bis-2,2,2-trichloroethyl acetal, bis-2,2,2-trichloroethyl ketal,diacetyl acetal and diacetyl ketal; cyclic acetals and ketals such as1,3-dioxane, 5-methylene-1,3-dioxane, 5,5,-dibromo-1,3-dioxane,1,3-dioxolane, 4-bromomethyl-1,3-dioxolane, 4-3′-butenyl-1,3-dioxolaneand 4,5-dimethoxymethyl-1,3-dioxolane; cyanohydrins such asO-trimethylsilyl cyanohydrin, O-1-ethoxyethyl cyanohydrin andO-tetrahydropyranyl cyanohydrin; and leaving alicyclic skeletons such astertiary alicylic esters having alkyl groups.

It is preferable to make the percentage of the dissolution-preventivegroup approximately 35 to 65 mol % of the resin. This value isconsiderably greater than the percentage of a dissolution-preventivegroup introduced to a conventional acrylic polymer. For this reason, theresin of the invention has high dissolution contrast as compared withconventional acrylic resists. Moreover, a pattern formed by using theresin of the present invention can be developed with high resolution bya standard developer such as a 2.38% aqueous solution oftetramethylammonium hydroxide (TMAH).

The resin according to the present invention may contain in its moleculea dissolution-preventive group and an alkali-soluble group at the sametime. Such a resin can show the two functions of alkali-solubility anddissolution-preventing properties.

Examples of alkali-soluble groups include carboxyl group and phenolichydroxyl group.

In this case, it is preferable to make the percentage of thedissolution-preventive group approximately 10 to 80 mol % of the resin.When this percentage is less than 10 mol %, the dissolution-preventingfunction cannot be revealed, and the unexposed area is also dissolved.It is thus impossible to attain the resolution of a pattern. On theother hand, when the above percentage is in excess of 80 mol %, theresin has extremely decreased adhesion, so that it is difficult to forma pattern. Moreover, the resist composition shows extremely highhydrophobicity and repels a developer, so that a pattern cannot beformed.

Further, in this case, the percentage of the alkali-soluble group in theresin be so made that it will be 20 mol % or more in the area that willbe removed by development to be conducted after exposure/PEB (postexposure bake). When the percentage of the alkali-soluble group in thisarea is made less than 20 mol %, the alkali developability becomesworse.

In the case where one alicyclic unit contains both adissolution-preventive group, and a polar group such as hydroxyl groupthat can improve adhesion, the above-described problem of adhesion isnot brought about. Therefore, in this case, it is possible to introducea dissolution-preventive group to an extent of 80 mol % or more.

In the resist composition of the present invention, it is desirable thatnot only the resin but also a part of the structure of an additive(dissolution-preventive agent), which will be described later, has theabove-described group decomposable by an acid, the alkali-soluble groupcontained in this group being protected.

When a water-soluble compound is polymerized to obtain a resin accordingto the present invention, the resulting resin has improvedalkali-solubility. However, such a resin requires the use of a thindeveloper, so that the use of a water-soluble compound is undesirable.In the resin according to the present invention, it is preferable thatthe proportion of a vinyl compound having high water-solubility of morethan 0.1 g/g water is as low as possible, and it is most preferable thatthe resin does not contain such a compound. The proportion of a compoundwhose water-solubility is in excess of 0.1 g/g water is at most 0 to 20%by weight of the polymer.

To make a resin according to the present invention by polymerization, itis preferable to use a compound having no molecular skeleton whose lightabsorption in short-wavelength ranges is high, such as benzene nucleus,from the viewpoint of the transparency of the resulting resist againstshort-wavelength light. Specifically, it is desirable that theabsorbance of the resin against light having a wavelength of 193 nm be 4or less per 1 micrometer.

<Photo Acid Generator>

Examples of photo acid generators useful for resist compositions of thepresent invention include the following compounds: aryl onium salts,naphthoquinonediazide compounds, diazonium salts, sulfonate compounds,sulfonium compounds, sulfamide compounds, iodonium compounds andsulfonyldiazomethane compounds. Specific examples of these compoundsinclude triphenylsulfonium triflate, diphenyliodonium triflate,2,3,4,4-tetrahydroxy-benzophenone-4-naphthoquinonediazidesulfonate,4-N-phenylamino-2-methoxyphenyldiazoniumsulfate,4-N-phenylamino-2-methoxyphenyldiazonium p-ethylphenylsulfate,4-N-phenylamino-2-methoxyphenyldiazonium 2-naphthylsulfate,4-N-phenylamino-2-methoxyphenyldiazoniumphenylsulfate,2,5-diethoxy-4-N-4′-methoxyphenylcarbonylphenyldiazonium3-carboxy-4-hydroxyphenyl sulfate, 2-methoxy-4-N-phenylphenyldiazonium3-carboxy-4-hydroxyphenylsulfate, diphenylsulfonylmethane,diphenylsulfonyldiazomethane, diphenyldisulfone,alpha-methylbenzointosylate, pyrogallol trimesylate, benzointosylate,MPI-103 (manufactured by Midori Kagaku Co., Ltd., Japan, CAS No.87709-41-9), BDS-105 (manufactured by Midori Kagaku Co., Ltd., CAS No.145612-66-4), NDS-103 (manufactured by Midori Kagaku Co., Ltd., CAS No.110098-97-0), MDS-203 (manufactured by Midori Kagaku Co., Ltd., CAS No.127855-15-5), Pyrogallol tritosylate (manufactured by Midori Kagaku Co.,Ltd., CAS No. 20032-64-8), DTS-102 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 75482-18-7), DTS-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 71449-78-0), MDS-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 127279-74-7), MDS-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 116808-67-4), MDS-205 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 81416-37-7), BMS-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 149934-68-9), TMS-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 127820-38-6), NB-101 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 20444-09-1), NB-201 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 4450-68-4), DNB-101 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 114719-51-6), DNB-102 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 131509-55-2), DNB-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 132898-35-2), DNB-104 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 132898-36-3), DNB-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 132898-37-4), DAM-101 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 1886-74-4), DAM-102 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 28343-24-0), DAM-103 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 14159-45-6), DAM-104 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 130290-80-1), (manufactured by Midori Kagaku Co., Ltd.,CAS No. 130290-82-3), DAM-201 (manufactured by Midori Kagaku Co., Ltd.,CAS No. 28322-50-1), CMS-105 (manufactured by Midori Kagaku Co., Ltd.),DAM-301 (manufactured by Midori Kagaku Co., Ltd., CAS No. 138529-81-4),SI-105 (manufactured by Midori Kagaku Co., Ltd., CAS No. 34694-40-7),NDI-105 (manufactured by Midori Kagaku Co., Ltd., CAS No. 133710-62-0),and EPI-105 (manufactured by Midori Kagaku Co., Ltd., CAS No.135133-12-9). Moreover, the following compounds may also be used.

wherein C₁ and C₂ form single bond or double bond, R₁₀ is hydrogen atom,fluorine atom, or an alkyl or aryl group which may be substituted withfluorine atom, and R₁₁ and R₁₂, which may be the same or different,respectively represent a monovalent organic group, and may be combinedwith each other to form a cyclic structure.

wherein Z represents an alkyl group.

Of the above-enumerated photo acid generators, conjugated polycyclicaromatic compounds having naphthalene or dibenzothiophene skeleton, suchas aryl onium salts, sulfonate compounds, sulfonyl compounds andsulfamide compounds are advantageous from the viewpoints of transparencyagainst short-wavelength light, and of heat resistance. Specifically,the following compounds are preferred: sulfonyl or sulfonate compoundshaving naphthalene, pentalene, indene, azulene, heptalene, biphenylene,as-indacene, s-indacene, acenaphthylene, fluorene, phenalene,phenanthrene, anthracene, fluorantene, acephenanthrylene, aceanthrylene,triphenylene, pyrene, chrysene, naphthacene, pleiadene, picene,perylene, pentaphene, pentacene, tetraphenylene, hexaphene, hexacene,rubicene, coronene, trinaphthylene, heptaphene, heptacene, pyranthrene,ovalene, dibenzophenanthrene, benz[a]anthracene, dibenzo[a,j]anthracene,indeno[1,2-a]indene, anthra[2,1-a]naphthacene or1H-benzo[a]cyclopent[j]anthracene ring; 4-quinonediazide compoundshaving naphthalene, pentalene, indene, azulene, heptalene, biphenylene,as-indacene, s-indacene, acenaphthylene, fluorene, phenalene,phenanthrene, anthracene, fluorantene, acephenanthrylene, aceanthrylene,triphenylene, pyrene, chrysene, naphthacene, pleiadene, picene,perylene, pentaphene, pentacene, tetraphenylene, hexaphene, hexacene,rubicene, coronene, trinaphthylene, heptaphene, heptacene, pyranthrene,ovalene, dibenzophenanthrene, benz[a]anthracene, dibenzo[a,j]anthracene,indeno[1,2-a]indene, anthra[2,1-a]naphthacene or1H-benzo[a]cyclopent[j]anthracene ring; and salts with triflates ofsulfoniums or iodoniums having, as side chain, naphthalene, pentalene,indene, azulene, heptalene, biphenylene, as-indacene, s-indacene,acenaphthylene, fluorene, phenalene, phenanthrene, anthracene,fluorantene, acephenanthrylene, aceanthrylene, triphenylene, pyrene,chrysene, naphthacene, pleiadene, picene, perylene, pentaphene,pentacene, tetraphenylene, hexaphene, hexacene, rubicene, coronene,trinaphthylene, heptaphene, heptacene, pyranthrene, ovalene,dibenzophenanthrene, benz[a]anthracene, dibenzo[a,j]anthracene,indeno[1,2-a]indene, anthra[2,1-a]naphthacene or1H-benzo[a]cyclopent[j]anthracene ring In particular, sulfonyl orsulfonate compounds having naphthalene or anthracene ring;4-quinonediazide compounds having naphthalene or anthracene ring towhich hydroxyl group has been introduced; and salts with triflates ofsulfoniums or iodoniums having as side chain naphthalene or anthracenering.

Of these photo acid generators, triphenylsulfonium triflate,diphenyliodonium triflate, trinaphthylsulfonium triflate,dinaphthyliodonium triflate, dinaphthylsulfonyl methane, NAT-105(manufactured by Midori Kagaku Co., Ltd., CAS No. 137867-61-9), NAT-103(manufactured by Midori Kagaku Co., Ltd., CAS. No. 131582-008), NAI-105(manufactured by Midori Kagaku Co., Ltd., CAS No. 85342-62-7), TAZ-106(manufactured by Midori Kagaku Co., Ltd., CAS No. 69432-40-2), NDS-105(manufactured by Midori Kagaku Co., Ltd.), PI-105 (manufactured byMidori Kagaku Co., Ltd., CAS No. 41580-58-9), s-alkylateddibenzothiophene triflate, and s-fluoroalkylated dibenzothiophenetriflate (manufactured by Daikin Industries, Ltd., Japan) are preferablyused. Of these compounds, triphenylsulfonium triflate,trinaphthylsulfonium triflate, dinaphthyliodonium triflate,dinaphthylsulfonyl methane, NAT-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 137867-61-9), NDI-105 (manufactured by Midori Kagaku Co.,Ltd., CAS No. 133710-62-0), and NAI-105 (manufactured by Midori KagakuCo., Ltd., CAS No. 85342-62-7) are particularly preferred.

In the resist composition of the present invention, the amount of thephoto acid generator to be incorporated is from 0.001 to 50% by weight,more preferably from 0.01 to 40% by weight, most preferably from 0.1 to20% by weight of the total amount of the other solid components. Whenthis amount is less than 0.001% by weight, it is difficult to form aresist pattern at high sensitivity. On the other hand, when this amountis in excess of 50% by weight, the resulting resist film may haveimpaired mechanical strength.

<Other Components>

The resist composition of the present invention may further comprisedissolution-preventive agents, alkali-soluble resins, and resinouscompounds whose alkali-solubility is increased when irradiated.

Dissolution-preventive agents will be described hereinafter.

A resin according to the present invention, which is insoluble inalkalis, becomes alkali-soluble by being decomposed by an acid catalystthat is generated from the photo acid generator incorporated into theresin when light is applied to the generator. It is therefore notessential to introduce a dissolution-preventive group into the resin, orto add a dissolution-preventive agent to the resist composition.However, in order to obtain a great difference in dissolution ratebetween exposed area and unexposed area, it is preferable to introduce adissolution-preventive group into the resin, or to add adissolution-preventive agent to the resin composition.

Among the compounds described in, for example, U.S. Pat. No. 4,491,628and U.S. Pat. No. 4,603,101, and Japanese Patent Laid-Open PatentPublication No. 27829/1988, those ones whose aromatic rings are thecondensed polycyclic aromatic rings can be used asdissolution-preventive compounds which can serve as thedissolution-preventive agents. Alternatively, those compounds containingcondensed polycyclic aromatic ring skeleton having carboxylic acids orphenolic hydroxyl groups can be used if a part of or all of the hydroxylends are substituted with protective groups decomposable by an acid.

Examples of the above protective groups include tert-butyl ester,tert-butyl carbonate, tetrahydropyranyl group and acetal group.

Specific examples of such compounds include tert-butyl carbonates ofnaphthalene, anthracene, and polyhydroxy compounds, tert-butyl carbonateof naphthol phthalein, quinazarine, quinizarine, tert-butyl carbonatesof naphthol novolak resins.

The amount of this compound to be incorporated into the resistcomposition is desirably at least 3% by weight and less than 40% byweight of the polymer. When the amount of this compound to be added ismade less than 3% by weight, the effects of the compound cannot beobtained, or the lowering of resolution is brought about. On thecontrary, when this amount is made more than 40% by weight, the coatingperformance or dissolution rate is drastically decreased. In general, itis more desirable that this amount be from 10 to 30% by weight.

In the case where the resist composition contains adissolution-preventive agent, the resin is not always necessary to havea dissolution-preventive group. In this case, the resin may be onecopolymerized with a vinyl compound having an alkali-soluble group, suchas methacrylic acid, capable of imparting alkali-solubility to thecopolymer. Examples of dissolution-preventive agents include compoundsdecomposable by an acid, which can sufficiently showdissolution-preventing ability in alkaline solutions and whosedecomposition products can produce, in alkaline solutions, —(C═O)O—,—OS(═O)₂— or —O—. Specific examples of these compounds includet-butoxycarbonyl ether, tetrahydropyranyl ether,3-bromotetrahydropyranyl ether, 1-methoxycyclohexyl ether,4-methoxy-tetrahydropyranyl ether, 1,4-dioxane-2-yl ether,tetrahydrofuranyl ether,2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ylether, t-butyl ether, trimethylsilyl ether, triethylsilyl ether,triisopropylsilyl ether, dimethylisopropylsilyl ether,diethylisopropylsilyl ether, dimethylsesquisilyl ether ort-butyldimethylsilyl ether of phenolic compounds, meldrum acidderivatives, and the like. Of these, those compounds obtained byprotecting the hydroxyl group of phenolic compounds by t-butoxycarbonyl,t-butoxycarbonylmethyl, trimethylsilyl, t-butyldimethylsilyl ortetrahydropyranyl group, those compounds obtained by adding meldrum acidto naphthaldehyde, and those compounds obtained by adding meldrum acidto aldehydes having alicyclic structure are preferred.

Moreover, the dissolution-preventive agent may be isopropyl ester,tetrahydropyranyl ester, tetrahydrofuranyl ester, methoxyethoxymethylester, 2-trimethylsilylethoxymethyl ester, t-butyl ester, trimethylsilylester, triethylsilyl ester, t-butyldimethylsilyl ester,isopropyldimethylsilyl ester, di-t-butylmethylsilyl ester, oxazole,2-alkyl-1,3-oxazoline, 4-alkyl-5-oxo-1,3-oxazoline,5-alkyl-4-oxo-1,3-dioxolane or the like of polyvalent carboxylic acids.In addition, there can also be mentioned compounds represented by thefollowing formula.

Of these dissolution-preventive agents, conjugated polycyclic aromaticcompounds are preferable in the present invention because thesecompounds are excellent in transparency against short-wavelength light.Light absorption bands are shifted to shorter wavelength regions inthese compounds due to the stabilization of conjugation of pi electrons.Therefore, in the present invention, it is possible to obtain a resisthaving excellent transparency against short-wavelength light andsufficiently high heat resistance by using especially a conjugatedphenolic aromatic compound as the dissolution-preventive agent.

For the alkali-soluble resins included in the above-described othercomponents of the resist composition of the present invention, any resincan be used as long as it is basically alkali-soluble. Preferableexamples of such resins include those ones useful for known ArF resists,and they may have the functions of chemically amplified resists.

Further, the resist composition of the present invention may form anegative image when a resin having acid anhydride structure is processedas the resin component at a high temperature, or when hydroxyl group isattached to the specific tertiary carbon atom of the resin component,such hydroxyl group being readily underwent dehydration condensationreaction by an acid catalyst. By taking advantage of this action, anegative image may be formed.

The resist composition of the present invention is, in general, preparedas a varnish by dissolving a resin component, a photo acid generator, adissolution-preventive agent, a cross-linking agent, an alkali-solubleresin and the like in an organic solvent, and filtering the solution.The resist for alkali development according to the present invention mayfurther contain the following agents and compounds: other polymers suchas epoxy resins, polymethyl methacrylate, polymethyl acrylate,polymethyl methacrylate, propylene oxide-ethylene oxide copolymers andpolystyrene, amine compounds useful for improving environmentalresistance, basic compounds such as pyridine derivatives, surface activeagents useful as film modifiers, and reflection-preventive agents.

Examples of the organic solvent herein used include ketone solvents suchas cyclohexane, acetone, methyl ethyl ketone and methyl isobutyl ketone,cellosolve solvents such as methyl cellosolve, methyl cellosolveacetate, ethyl cellosolve acetate and butyl cellosolve acetate, estersolvents such as ethyl acetate, butyl acetate, isoamyl acetate andgamma-butyrolactone, glycol solvents such as propylene glycol monomethylether acetate, dimethyl sulfoxide, and nitrogen-containing solvents suchas hexamethylphosphoric triamide dimethylformamide andN-methylpyrrolidone. Besides the above solvents, solvent mixturesobtained by adding dimethyl sulfoxide, dimethylformaldehyde,N-methylpyrrodinone or the like to the above-enumerated solvents inorder to improve the solubility may also be used. Further, propionicacid derivatives such as methyl methylpropionate, lactic esters such asethyl lactate, PGMEA (propylene glycol monomethyl ether acetate) and thelike do not have high toxicity, so that they can also be favorably used.Of these, PGMEA and ethyl lactate are particularly preferred becausethey are highly soluble in the resins of the present invention.

In the present invention, these solvents may be used either singly or incombination of two or more members. Moreover, the solvent may furthercontain an aliphatic alcohol such as isopropyl alcohol, ethyl alcohol,methyl alcohol, butyl alcohol, n-butyl alcohol, s-butyl alcohol, t-butylalcohol or isobutyl alcohol, or an aromatic solvent such as toluene orxylene. When the resist composition of the present invention has acidanhydride structure, it shows high reactivity if the solvent containshydroxyl group, and thus loses its stability. In this case, therefore,the solvent is desirably one having no OH group.

Next, a pattern forming process using a resist composition of thepresent invention will be described hereinafter by referring to the casewhere the resist is a chemically amplified positive resist. First ofall, a varnish prepared by dissolving the resist in an organic solventin the above-described manner is coated onto a predetermined substrateby means of spin coating or dipping. Thereafter, the varnish coated ontothe substrate is dried at a temperature of 150° C. or lower, preferablyfrom 70 to 120° C. to form a resist film. Examples of the substrateuseful herein include silicon wafers, silicon wafers whose surfaces areprovided with various insulating films, electrodes and lines, blankmasks, semiconductor wafers made from compounds belonging to the groupsIII to V such as GaAs or AlGaAs, masks on which chrome or chrome oxideis vacuum-deposited, aluminum-deposited substrates, BPSG-coatedsubstrates, PSG-coated substrates, BSG-coated substrates, SOG-coatedsubstrates, and carbon-film-sputtered substrates.

Subsequently, actinic radiation is applied to the resist film through apredetermined mask pattern, or directly scanned on the surface of theresist film, thereby exposing the resist film to light. As mentionedpreviously, the resist of the present invention for alkali developmenthas excellent transparency against not only short-wavelength light butalso light of wide wavelength regions. It is therefore possible to useas the actinic radiation ultraviolet rays, X-rays, the i-, h-, or g-raysof a low-pressure mercury vapor lamp, light emitted by a xenon lamp,deep UV light such as KrF, ArF, or F₂ excimer laser light, synchrotronorbital radiation (SOR), electron beams (EB), gamma rays, ion beams orthe like.

In particular, in the case of a chemically amplified resist, the resistfilm is subjected to baking treatment at a temperature of approximately170° C. or lower by heating the resist film on a hot plate or in anoven, or by applying infrared light to the resist film. Thereafter, theresist film is developed by means of dipping or spraying to selectivelydissolve it in an alkaline solution, thereby removing the exposed areaor unexposed area of the resist film to form a desired resist pattern.Specific examples of the alkaline solution that can be used hereininclude aqueous organic alkaline solutions such as an aqueoustetramethylammonium hydroxide solution and an aqueous choline solution,aqueous inorganic alkaline solutions such as an aqueous potassiumhydroxide solution and an aqueous sodium hydroxide solution, andsolutions obtained by adding alcohols, surface active agents or the liketo these solutions. It is preferable that the concentration of thealkaline solution be 15% by weight or less in order to obtain asufficient difference in dissolution rate between the exposed area andthe unexposed area.

The resist pattern thus formed by the use of the resist composition ofthe present invention is extremely excellent in resolution. For example,when dry etching is conducted by using this resist pattern as an etchingmask, an extremely fine pattern at a quarter micron level can betransferred to the bare substrate with high fidelity. The resist patternherein obtained shows high dry-etching resistance because, even when oneof C—C bond in the alicyclic structure contained in the polymercompound, base resin, is broken, the other bond can remain.

Any step other than the above-described steps may be added to thepattern forming process of the present invention. For example, it ispossible to properly add the step of forming a planarizing layer as theground layer of the resist film, the step of pretreatment to be carriedout in order to improve the adhesion between the resist film and thesubstrate, the step of rinsing to be carried out after developing theresist film for removing the developer by using water or the like, andthe step of re-applying ultraviolet light before conducting dry etching.

EXAMPLES

The present invention will now be explained more specifically byreferring to the following examples.

Synthesis Example I-1

6.0 g of 2-(3-carboxy-1-adamantyl)-2-propyl acrylate was mixed with 20 gof tetrahydrofuran (THF). To this mixture was added 0.20 g ofazo-isobutyro-nitrile (AIBN), and the mixture was heated at 60° C. for35 hours with stirring. The reaction solution was added dropwise ton-hexane. The precipitate was collected by filtration, and dried toobtain a copolymer represented by the following chemical formula, havinga weight-average molecular weight (calculated in terms of styrene) ofapproximately 5,000.

Synthesis Example 1-2

50 mol % of 2-(3,7-dimethyl-4-adamantanon-1-yl)-2-propyl acrylate and 50mol % of 3-(3-hydroxy-1-adamantyl)-3-pentyl acrylate, the total amountbeing 6.0 g, were mixed with 20 g of THF. To this mixture was added 0.20g of AIBN, and the mixture was heated at 60° C. for 35 hours withstirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately5,000.

Synthesis Example I-3

65 mol % of 1-(3-hydroxy-1-adamantyl)-1-propyl acrylate, 25 mol % oft-butyl acrylate and 10 mol % of methacrylic acid, the total amountbeing 6.0 g, were mixed with 20 g of THF. To this mixture was added 0.36g of AIBN, and the mixture was heated at 60° C. for 35 hours withstirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately8,000.

Synthesis Example 1-4

80 mol % of 3-(3-hydroxy-1-adamantyl)-3-pentyl acrylate and 20 mol % of4,6,6-trimethyl-2-oxepanon-4-yl acrylate, the total amount being 6.0 g,were mixed with 20 g of THF. To this mixture was added 0.20 g of AIBN,and the mixture was heated at 60° C. for 35 hours with stirring. Thereaction solution was added dropwise to n-hexane. The precipitate wascollected by filtration, and dried to obtain a copolymer represented bythe following chemical formula, having a weight-average molecular weight(calculated in terms of styrene) of approximately 7,000.

Synthesis Example I-5

60 mol % of 2-(3-hydroxy-1-adamantyl)-2-propyl acrylate, 30 mol % of5-acryloyloxy-2-adamantanone, and 10 mol % of methacrylic acid, thetotal amount being 6.0 g, were mixed with 20 g of THF. To this mixturewas added 0.18 g of AIBN, and the mixture was heated at 60° C. for 35hours with stirring. The reaction solution was added dropwise ton-hexane. The precipitate was collected by filtration, and dried toobtain a copolymer represented by the following chemical formula, havinga weight-average molecular weight (calculated in terms of styrene) ofapproximately 7,000.

Synthesis Example I-6

70 mol % of 2-(3-hydroxy-1-adamantyl)-2-propyl acrylate, 20 mol % of2-vinyl naphthalene, and 10 mol % of methacrylic acid, the total amountbeing 6.0 g, were mixed with 20 g of THF. To this mixture was added 0.18g of AIBN, and the mixture was heated at 60° C. for 35 hours withstirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately7,000.

Synthesis Example I-7

50 mol % of 2-(3-hydroxy-1-adamantyl)-2-propyl acrylate, and 50 mol % ofmaleic anhydride, the total amount being 6.0 g, were mixed with 20 g ofTHF. To this mixture was added 0.18 g of AIBN, and the mixture washeated at 75° C. for 24 hours with stirring. The reaction solution wasadded dropwise to methanol to coagulate the copolymer. The copolymer wasdissolved in THF again, and the solution was added dropwise to n-hexane.The precipitate was collected by filtration, and dried to obtain acopolymer represented by the following chemical formula, having aweight-average molecular weight (calculated in terms of styrene) ofapproximately 4,000.

Synthesis Example I-8

70 mol % of 2-(3,3-dimethtyl-3-hydroxy-1-adamantyl)-2-probylmethacrylate, and 30 mol % of tetrahydropyranyl methacrylate, the totalamount being 6.0 g, were mixed with 20 g of THF. To this mixture wasadded 0.18 g of AIBN, and the mixture was heated at 60° C. for 35 hourswith stirring. The reaction solution was added dropwise to n-hexane. Theprecipitate was collected by filtration, and dried to obtain a copolymerrepresented by the following chemical formula, having a weight-averagemolecular weight (calculated in terms of styrene) of approximately6,000.

Synthesis Example I-9

60 mol % of 2-(3-tetrahydropyranyloxycarbonyl-1-adamantyl)-2-propylacrylate, and 40 mol % of 1-methacryloyloxy-3-hydroxyadamantane, thetotal amount being 6.0 g, were mixed with 20 g of THF. To this mixturewas added 0.18 g of AIBN, and the mixture was heated at 60° C. for 35hours with stirring. The reaction solution was added dropwise ton-hexane. The precipitate was collected by filtration, and dried toobtain a copolymer represented by the following chemical formula, havinga weight-average molecular weight (calculated in terms of styrene) ofapproximately 6,000.

Synthesis Example I-10

70 mol % of carboxytricyclododecyl acrylate, and 30 mol % ofethoxyethoxycarbonyltricyclododecyl methacrylate, the total amount being6.0 g, were mixed with 20 g of THF. To this mixture was added 0.18 g ofAIBN, and the mixture was heated at 60° C. for 35 hours with stirring.The reaction solution was added dropwise to n-hexane. The precipitatewas collected by filtration, and dried to obtain a copolymer representedby the following chemical formula, having a weight-average molecularweight (calculated in terms of styrene) of approximately 15,000.

Synthesis Example I-11

50 mol % of 2-adamantyl-2-propyl methacrylate, and 50 mol % mevaloniclactone methacrylate, the total amount being 6.0 g, were mixed with 20 gof THF. To this mixture was added 0.18 g of AIBN, and the mixture washeated at 60° C. for 35 hours with stirring. The reaction solution wasadded dropwise to n-hexane. The precipitate was collected by filtration,and dried to obtain a copolymer represented by the following chemicalformula, having a weight-average molecular weight (calculated in termsof styrene) of approximately 11,000.

Example I-1

To the polymer obtained in Synthesis Example I-1 was addedtriphenylsulfonium triflate in an amount of 1% by weight of the polymer.This composition was made into a 10 wt % ethyl lactate solution. Afterfiltering through a 0.2 micron membrane filter, the solution wasspin-coated onto a silicon wafer which had been treated with hexamethyldisilazane, and pre-baked at 120° C. for 90 seconds to form a film witha thickness of 0.2 micrometers. This film was exposed to ArF excimerlaser (NA=0.55) light. Thereafter, the wafer was baked at 110° C. for 60seconds, and then developed by a 2.38% aqueous solution oftetramethylammonium hydroxide for 60 seconds. As a result, theresolution with an L/S of 0.25 micrometers was attained at an exposureenergy of 3.5 mJ/cm².

According to optical-microscopic observations, no peeling of the patternwas confirmed, and the adhesion between the film and the substrate wasalso found to be excellent. Moreover, any residue called scum whichtends to be formed when development is conducted was not observed.

Examples 1-2 to I-9 and Comparative Examples I-1 and I-2

To the respective polymers obtained in Synthesis Examples 2 to 9 andSynthesis Examples 10 and 11, triphenylsulfonium triflate was added inan amount of 1% by weight of the polymer. The compositions obtained wererespectively dissolved in proper solvents. By using these solutions,pattern formation was conducted in the same manner as in Example I-1.The results are shown in Table I-1. TABLE I-1 Post Exposure DevelopmentExposure Baking TMAH Adhesion Energy Temp. Time conc. TimeDevelopability to (mJ/cm²) (° C.) (sec) (wt %) (sec) (μmL/S) substrateScum Ex. I-1 3.5 110 60 2.38 60 0.25 Not formed Ex. I-2 3.6 110 60 2.3855 0.24 Not formed Ex. I-3 8.8 110 60 2.38 40 0.17 Not formed Ex. I-44.7 110 60 2.38 45 0.15 Not formed Ex. I-5 6.8 110 60 2.38 40 0.17 Notformed Ex. I-6 7.8 110 60 2.38 50 0.17 Not formed Ex. I-7 4.5 110 601.15 40 0.15 Not formed Ex. I-8 3.9 110 60 2.38 40 0.16 Not formed Ex.I-9 4.7 110 60 2.38 90 0.15 Not formed Comp. Ex. 11.0 70 60 2.38 60 0.16Slightly I-1 formed Comp. Ex. 5.5 110 60 2.38 90 0.16 x Formed I-2

As is clear from the data shown in the above table, the resistcompositions of the present invention were superior to that ofComparative Example I-1 in sensitivity and developability. The resist ofComparative Example I-2 was poor in adhesion to the substrate, and afine pattern could not be formed unless a ground film was provided onthe substrate beforehand. Moreover, this resist formed scum, like theresist of Comparative Example I-1, when development was conducted. Theresist compositions of the present invention were also excellent in thispoint.

Production Example 1 of Semiconductor Device

By referring now to the accompanying drawings, a method for producingsemiconductor devices, using the resist compositions and pattern formingprocess of the present invention will now be explained.

FIG. 1 is a cross-sectional view showing one example of a process forproducing a semiconductor chip by using the resist composition of thepresent invention.

As shown in FIG. 1(a), a silicon oxide film with a thickness ofapproximately 0.8 micrometers was formed as an etching film on a siliconsemiconductor substrate 1 by CVD. On top of this film, a resist film 3with a thickness of approximately 0.3 micrometers, comprising the resistcomposition of Example I-1 was formed.

This resist film 3 was patterned by the above-described method to form apattern composed of open holes, each having a diameter of 0.3micrometers. The resist pattern 3 a obtained was heated at 130° C. for30 minutes in nitrogen atmosphere. The silicon oxide etching film 2 wasselectively etched by RIE using CF₄gas, and, as an etching mask, theabove-obtained resist pattern 3A to conduct pattern transfer as shown inFIG. 1(b).

Finally, the resist pattern 3A was carbonized and removed by O₂ plasmato obtain the silicon oxide film 2 having fine open holes 6 as shown inFIG. 1(c). The diameter of the fine open hole 6 formed in the siliconoxide film 2 is 0.32 micrometers, and the scattering in the thicknessesof the film was below 2%.

Production Example 2 of Semiconductor Device

As shown in FIG. 2(a), a silicon oxide film 2 with a thickness of 0.8micrometers was formed on a semiconductor substrate 1 by CVD. In thesemiconductor substrate 1, MOSFET, a diode and other elements (not shownin the figure), for example, had been formed in advance. Subsequently, alower wiring layer 10 composed of Al—Si—Cu, having a thickness ofapproximately 0.3 micrometers, and an interlayer insulating layer 7 madefrom SiO₂, having a thickness of 0.5 micrometers were formed. On theselayers was formed an upper wiring layer 11 composed of Al—Si—Cu, havinga thickness of approximately 0.3 micrometers. At this time, a step ofapproximately 0.2 micrometers was formed in the upper wiring layer. Aresist film 3 with a thickness of 0.3 micrometers, comprising the resistcomposition was further formed on the upper wiring layer 11 in the samemanner as in Production Example 1 of Semiconductor Device.

This resist film was patterned in the same manner as in ProductionExample 1 of Semiconductor Device to form a resist pattern. By usingthis pattern as an etching mask, the upper wiring layer 11 was removedby RIE, using a chlorine gas such as CCl₄ to obtain an upper wiringlayer 11A as shown in FIG. 2(b).

Finally, the resist pattern 3A was carbonated and removed by O₂ plasmato obtain two-layered wiring as shown in FIG. 2(c).

Production Example 3 of Semiconductor Device

FIG. 3 is a cross-sectional view showing a case where the presentinvention is applied to the formation of Au wiring.

First of all, a silicon oxide film 2 with a thickness of approximately0.8 micrometers was formed on a semiconductor substrate 1 by CVD. In thesemiconductor substrate 1, MOSFET, a diode and other elements (not shownin the figure), for instance, had been formed beforehand. Subsequently,on top of this silicon oxide film 2, a titanium-containing tungsten(Ti—W) film 12 with a thickness of approximately 0.2 micrometers, and agold (Au) film 13 with a thickness of approximately 0.1 micrometers wereformed successively. A resist film having a thickness of approximately0.3 micrometers, containing the same resist composition as in ProductionExample 1 of Semiconductor Device was further formed on the Au film.

This resist film 3 was patterned in the same manner as in ProductionExample 1 of Semiconductor Device to form a resist pattern 3A as shownin FIG. 3(b), thereby making a groove. By using the Ti—W film 12 and Aufilm 13 bared at the bottom of the groove as electrodes, an Au platingfilm 14 with a thickness of 1 micrometer was formed in the groove byelectroplating.

Subsequently, the resist film 3A was carbonated and removed by O₂ plasmato make the Au plating film 14 project from the Au film 13 as shown inFIG. 3(c). Finally, the bare Au film 13 was removed by ion milling, andthe bare Ti—W film 13 was removed by the use of a fluorine gas to forman Au wiring 20 as shown in FIG. 3(d).

Example II-1

1-Acryloyl-3-hydroxyadamantane and tetrahydropyranyl methacrylate wereused as monomers. They were mixed with each other in one of the mixingratios shown in Table II-1, the total amount of the monomers being 0.05mol. This mixture was dissolved in 20 g of THF. To this solution wasadded 0.0125 mol of azobisbutyronitrile (AIBN) as a polymerizationinitiator. In argon atmosphere, the mixture was subjected three times tofreezing deaeration at a temperature of liquid nitrogen, followed byreaction at 60° C. for 30 hours. To this reaction solution was added 2ml of methanol to terminate the reaction. The reaction solution wasadded dropwise to 250 g of hexane with stirring for reprecipitation. Thesolution was filtered through a glass filter, and the solid mattercollected was vacuum-dried at 60° C. for three days. In this manner, sixdifferent resins were obtained.

The molecular weights of the resins obtained, calculated in terms ofpolystyrene, were in the range of 3,500 to 8,000. The Mw/Mn ratios werefound to be from 1.7 to 1.9. The mixing ratio of the monomers in eachresin was determined by NMR. As a result, it was within ±2% of the ratioof the monomers at the time when they were charged.

To 1.0 g of the respective resins obtained was added 0.05 g oftriphenylsulfonium triflate as a photo acid generator. The mixtures wererespectively dissolved in 4.2 g of ethyl lactate to obtain six differentResists 1 to 6.

These six resist solutions were respectively spin-coated onto siliconwafers at 3,000 rpm for 30 seconds. Thereafter, the silicon wafers weresubjected to pre-exposure bake on a hot plate at 120° C. for 90 seconds.The thicknesses of the resist films were 0.5 micrometers. The resistfilms were exposed to ArF excimer laser light (wavelength 193 nm) toform a line & space pattern. The apparatus used for the exposure was anArF exposure system (NA=0.55, delta=0.7) manufactured by Nikon Corp.,Japan.

The patterned resists were subjected to post-exposure bake at 100° C.for 180 seconds, and then developed by a 2.38% aqueous solution oftetramethylammonium hydroxide at 25° C. for 60 seconds. By this, theexposed area of each resist film was selectively dissolved and removed,and a positive pattern was formed. The sensitivities and degrees ofresolution of the resists are also shown in Table II-1. TABLE II-1Mixing Sensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) RemarksResist II-1 66:34 7.0 0.25 — Resist II-2 60:40 4.5 0.19 — Resist II-355:45 3.8 0.17 — Resist II-4 50:50 3.0 0.15 — Resist II-5 45:55 3.2 0.230.15 μmL/S when a protective film was used Resist II-6 40:60 3.4 0.300.15 μmL/S when a protective film was used

Example II-2

0.02 mol of 1-acryloyl-3-hydroxyadamantane, monomer, was homopolymerizedin the same manner as in Example I-1. The molecular weight of thehomopolymer, calculated in terms of the polystyrene, was 3,500, and theMw/Mn was 1.9.

Patterning was conducted in the same manner as in Example II-1 exceptthat the photo acid generator used in Example II-1 was changed tonaphthylimide campharsulfonate and that the post-exposure bake wascarried out at 160° C. As a result, it was confirmed that it waspossible to form a pattern although the L/S was as large as 0.45micrometers at an exposure energy of 42 mJ/cm². TABLE II-2 MixingSensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) Remarks Resist II-7— 42 0.45 —

Examples II-11 to II-15

Polymers were produced by the same method as in Example II-1 except thatthe 1-acryloyl-3-hydroxyadamantane used in Example II-1 was replaced by1-acryloyl-3-carboxyadamantan and that the mixing ratios used in ExampleII-1 were changed to those shown in Table II-3. By using these polymers,resists were prepared in the same manner as in Example II-1. Patterningwas conducted in the same manner as in Example II-1 by the use of theseresists. The results are shown in Table II-3. TABLE II-3 MixingSensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) Remarks ResistII-11 55:45 2.9 0.20 — Resist II-12 50:50 2.7 0.18 — Resist II-13 45:552.6 0.17 — Resist II-14 40:60 2.7 0.15 — Resist II-15 35:65 2.7 0.16 —

It is considered that why the optimum mixing ratios are different fromthose in Example II-1 is due to difference in acidity. It can be knownthat patterning can successfully be conducted by using these resists.

Example II-4

A polymer was made in the same manner as in Example II-1 except that amonomer mixture (molar ratio 1:1:2) of1-acryloyl-3-tert-butyloxycarbonyl adamantane,1-acryloyl-3-hydroxyadamantane and maleic anhydride was used instead ofthe monomers used in Example II-1. By the use of this polymer, a resistwas prepared in the same manner as in Example II-1. Patterning wasconducted in the same manner as in Example II-1 by using this resist. Asa result, it was confirmed that it was possible to form a pattern withan L/S of 0.17 micrometers at an exposure energy of 12 mJ/cm². Theresults are shown in Table II-4.

On the other hand, a polymer was made in the above-described manner byusing a monomer mixture (molar ratio 1:1:2) of2-acryloyl-7-tert-butyloxy-carbonyltricyclodecane,2-acryloyl-7-hydroxymethyltricyclodecane, and maleic anhydride. A resistwas prepared in the same manner as in the above by using this polymer,and then evaluated. It was impossible to form a pattern at all due tocross-linking reaction. It can thus be known that the resin having thestructure according to the present invention shows notable effects whenit contains an acid anhydride. TABLE II-4 Mixing Sensitivity ResolutionResist Ratio (mJ/cm²) (μmL/S) Remarks Resist II-16 1:1:2 12 0.17 —(“Mixing Ratio” denotes the molar ratio of1-acryloyl-3-tert-butyloxycarbonyladamantane:1-acryloyl-3-hydroxyadamantane:maleic anhydride at the timewhen they were charged.)

Example II-5

Polymers were produced in the manner as in Example II-1 except that the1-acryloyl-3-hydroxyadamantane used in Example II-1 was replaced with1-acryloyl-3-tetrahydropyranylcarboxyadamantane and1-acryloyl-3-hydroxyadamantane and that the mixing ratios used inExample II-1 were changed to those shown in Table II-5. By the use ofthese polymers, resists were prepared in the same manner as in ExampleII-1. Patterning was conducted in the same manner as in Example II-1 byusing these resists. The results are shown in Table II-5. TABLE II-5Mixing Sensitivity Resolution Resist Ratio (mJ/cm²) (μmL/S) RemarksResist II-21 60:40 6.8 0.17 — Resist II-22 55:45 5.8 0.17 — Resist II-2350:50 5.6 0.16 — Resist II-24 45:55 5.4 0.18 — Resist II-25 40:60 5.90.19 —(“Mixing Ratio” denotes the molar ratio of1-acryloyl-3-tetrahydropyranyl-carboxyadamantane to1-acryloyl-3-hydroxyadamantane at the time when they were charged.)

Example II-6

A mixture of 0.06 mol of Compound II-1 and 0.04 mol of Compound II-2 wassubjected to radical polymerization, using 0.01 mol of AIBN as apolymerization initiator to obtain Resin II-3 having a molecular weightof approximately 11,000. To 1.0 g of the resin obtained was added 0.01 gof triphenylsulfonium triflate as a photo acid generator, and themixture was dissolved in 10 g of PGMEA. The resist solution thusobtained was spin-coated onto a silicon wafer at 3,000 rpm for 30seconds, and then subjected to pre-exposure bake on a hot plate at 120°C. for 90 seconds. The thickness of the resist film formed was 0.2micrometers. This resist film was exposed to ArF excimer laser light toform a line & space pattern. This was then subjected to post-exposurebake at 130° C. for 90 seconds, and developed by a 2.38% aqueous TMAHsolution at 25° C. for 60 seconds, thereby obtaining a positive patternwith an L/S of 0.15 micrometers. The sensitivity was 7.0 mJ/cm².

Example II-7

A mixture of 0.04 mol of Compound II-1 and 0.06 mol of Compound II-4 wassubjected to radical polymerization, using 0.01 mol of AIBN as apolymerization initiator to obtain Resin II-5 having a molecular weightof approximately 10,000. To 1.0 g of the resin obtained was added 0.01 gof triphenylsulfonium triflate as a photo acid generator, and themixture was dissolved in 10 g of PGMEA. The resist solution thusobtained was spin-coated onto a silicon wafer at 3,000 rpm for 30seconds, and then subjected to pre-exposure bake on a hot plate at 120°C. for 90 seconds. The thickness of the resist film obtained was 0.2micrometers. This resist film was exposed to ArF excimer laser light toform a line & space pattern. This was then subjected to post-exposurebake at 110° C. for 90 seconds, and developed by a 2.38% aqueous TMAHsolution at 25° C. for 60 seconds, thereby obtaining a positive patternwith an L/S of 0.15 micrometers. The sensitivity was 30 mJ/cm².

Examples II-33-38

Polymer compounds II-12 to II-17 were obtained by radicallypolymerizing, as monomers, Compounds II-6 to II-11 and Compound II-2 or1-acryloyloxy-3-carboxyladamantane. The polymer compounds II-12 to II-17were respectively mixed with an acid generator TPS-105 (1 wt %), and themixtures were respectively dissolved in a PGMEA solution. Thesevarnishes obtained were respectively spin-coated onto silicon wafers.The films formed were exposed to light of 193 nm by using an ArF excimerlaser stepper, and baked at 110° C. for 5 minutes. The baked films werethen developed by a 0.36 N TMAH alkali developer, whereby the exposedarea remained, while the unexposed area was dissolved in the developer.Negative patterns were thus formed TABLE II-6

Sensitivity Resolution Example Polymer (mJ/cm²) (μmL/S) Ex. II-33Compound II-12 30 0.16 Ex. II-34 Compound II-13 33 0.16 Ex. II-35Compound II-14 35 0.18 Ex. II-36 Compound II-15 57 0.18 Ex. II-37Compound II-16 25 0.18 Ex. II-38 Compound II-17 60 0.17

From the data shown in the above table, it can be known that a negativepattern free from swelling can successfully be formed by the use of anyof these resists. Etching was conducted by using CF₄plasma. It was foundthat the etching rates of these resists were 1.2 to 1.0 time that ofpolyhydroxystyrene resin.

Examples II-9 to II-11 and Comparative Examples II-1 to II-5

The following homopolymers, Polymers 1 to 8, were obtained by radicallypolymerizing Monomers 1 to 8. The molecular weights of these polymerswere approximately 10,000.

The glass transition temperatures (Tg) of these polymers were measuredby a differential scanning calorimeter (DSC). The results are shown inTable II-7. TABLE II-7 Tg Found Tg Calcd. Polymer Ex. No. (° C.) (° C.)Polymer 1 Ex. II-9 160 156 Polymer 2 Comp. Ex. II-1 146 147 Polymer 3Comp. Ex. II-2 N.D. 146 Polymer 4 Comp. Ex. II-3 133 136 Polymer 5 Ex.II-10 159 156 Polymer 6 Comp. Ex. II-4 135 138 Polymer 7 Ex. II-11 154152 Poymer 8 Comp. Ex. II-5 130 129

As is clear from the date shown in Table II-7, Polymer 1 (Example II-9)in which hydroxyl group or an esterified group thereof is combined withcarbons at the two 3-position has a Tg about 10° C. higher than that ofPolymer 2 (Comparative Example II-41) or Polymer 3 (Comparative ExampleII-2) in which such a group is combined with only one tertiary carbonatom, and a Tg 20° C. higher than that of Polymer 4 (Comparative ExampleII-3) in which such a group is not combined with tertiary carbon atom atall.

Further, it can also be known that Polymer 5 (Example II-10) and Polymer7 (Example II-11) having different types of aliphatic rings, hydroxylgroup or an esterified group thereof being combined with carbons at thetwo 3-position, have higher glass transition temperatures.

Furthermore, the glass transition temperatures of these polymersobtained by calculation are also shown in Table II-7. The calculationwas conducted by the Bicerano method on the CAche system. The valuesobtained by this calculation are almost the same as those obtained bythe experiment. In the step of post-exposure bake that is an essentialstep in the processing of a chemically amplified resist, it is necessaryto bake the resist at a temperature of 100 to 150° C. At this time, whenthe Tg of the resist is low, a pattern cannot successfully be formed.Therefore, the resist compositions of the present invention, prepared byusing the polymers according to the present invention whose glasstransition temperatures are high can provide resist patterns with highresolution.

Test Example II-1

Monomer 1 and tetrahydropyranyl were polymerized to obtain a copolymer.This copolymer is quite the same as Resist II-4 that was used in ExampleII-1. By using this copolymer, a resist was prepared in the same manneras in Example II-1. Further, a copolymer of Monomer 2 andtetrahydropyranyl was obtained in the same manner as in Example II-1,and a comparative resist was prepared by using this copolymer. By theuse of these resists, exposure and processing were conducted in the samemanner as in Example II-1 to obtain resist patterns.

As a result, it was found the following: when the resist prepared byusing the copolymer with Monomer 1 was used, a pattern with an L/S of0.15 micrometers was obtained; while, when the resist prepared by usingthe copolymer with Monomer 2 was used, a pattern could not successfullybe obtained, and the L/S was only about 0.3 micrometers. The reason forthis is as follows: since the copolymer with Monomer 2 has a Tg lowerthan that of the copolymer with Monomer 1, the former copolymer becomesrubbery during the step of post-exposure bake, and the pattern wasfluidized.

Test Example II-2

50 mol % of monomer 5 and 50 mol % of tetrahydropyranyl were polymerizedto obtain a copolymer. The polymerization method was the same as that inExample II-1. By using this copolymer, a resist was prepared in the samemanner as in Example II-1. Further, in the same manner as in ExampleII-1, 50 mol % of Monomer 6 and 50 mol % of tetrahydropyranyl werepolymerized to obtain a copolymer, and a comparative resist was preparedby using this copolymer. By the use of these resists, exposure andprocessing were conducted in the same manner as in Example II-1 toobtain resist patterns.

As a result, it was found the following: when the resist prepared byusing the copolymer with Monomer 5 was used, a pattern with an L/S of0.16 micrometers was obtained at 5.2 mJ/cm²; while, when the resistprepared by using the copolymer with Monomer 6 was used, a pattern couldnot successfully be formed, and the L/S was only about 0.4 micrometers.

The reason for this is as follows: since the copolymer with Monomer 5has a Tg lower than that of the copolymer with Monomer 6, the formercopolymer becomes rubbery during the step of post-exposure bake, and thepattern was fluidized.

Test Example II-3

50 mol % of Monomer 7 and 50 mol % of tetrahydropyranyl were polymerizedtoobtaina copolymer. The polymerization method was the same as that inExample II-1. By using this copolymer, a resist was prepared in the samemanner as in Example II-1. Further, in the same manner as in ExampleII-1, 50 mol % of Monomer 8 and 50 mol % of tetrahydropyranyl werepolymerized to obtain a copolymer, and a comparative resist was preparedby using this copolymer. By the use of these resists, exposure andprocessing were conducted in the same manner as in Example II-1 toobtain resist patterns.

As a result, it was found the following: when the resist prepared byusing the copolymer with Monomer 7 was used, a pattern with an L/S of0.16 micrometers was formed at 5.2 mJ/cm²; while, when the resistprepared by using the copolymer with Monomer 6 was used, a pattern couldnot successfully be formed, and the L/S was only 0.4 micrometers.

The reason for this is as follows: since the copolymer with Monomer 8has a Tg lower than that of the copolymer with Monomer 7, the formercopolymer becomes rubbery during the step of post-exposure bake, and thepattern was fluidized.

Examples II-12 to II-16 and Comparative Example II-6

[Synthesis of Starting Compounds]

One mol of 1,3-dihydroxyadamantane was stirred in an acetic acid-aceticanhydride solution of CrO₃, oxidizing agent, with heating. Aftercarrying out the reaction for 8 hours, the reaction solution wasneutralized to obtain a mixture of polyhydroxylated compounds ofhydroxyadamantane. This mixture was partitioned by high performanceliquid chromatography to obtain 1,3,5-trihydroxyadamantane.

This 1,3,5-trihydroxyadamantane was dissolved in methylene chloride. Tothis solution were added a small amount of trimethylamine, and then anequimolar amount of trimethylsilyl chloride. Reaction was carried out atroom temperature. The reaction product was partitioned by highperformance liquid chromatography to obtain1,3-dihydroxy-5-trimethylsiloxyadamantane.

The 1,3-dicarboxyadamantane was oxidized and partitioned similarly toobtain 1,3-dicarboxy-5-hydroxyadamantane.

The 1,3-dicarboxy-5-hydroxyadamantane was dissolved in THF, and reactedwith an excessive amount of thionyl chloride under reflux for 4 hours.The excessive thionyl chloride and solvent were distilled off to obtain1,3-dichloroformyl-5-hydroxyadamantane, which was an acid chloridecompound of the 1,3-dicarboxy-5-hydroxyadamantane.

The 1,3-dichloroformyl-5-hydroxyadamantane was dissolved in methylenechloride. To this solution were added a small amount of trimethylamine,and then an equimolar amount of trimethylsilyl chloride. Reaction wascarried out at room temperature to obtain1,3-dichloroformyl-5-trimethylsiloxyadamantane.

[Synthesis of Resist Resins]

0.05 mol of the 1,3-dihydroxy-5-trimethylsiloxyadamantane was dissolvedin THF. To this solution were added 0.040 mol of the1,3-dichloroformyl-5-trimethylsiloxyadamantane, and then 0.010 mol of1,3-dicarboxyl-5-hydroxy-adamantane. The mixture was stirred whilekeeping its temperature at room temperature, and, to this, a solution of0.1 mol of triethylamine in THF was gradually added dropwise. Afterstirring two hours, the mixture was stirred at room temperature for afurther two hours. The reaction solution was filtered, and thengradually added dropwise to water for reprecipitation. The precipitatewas dissolved again in THF. By adding tetrabutylammonium fluoride (TBAF)to this solution, trimethylsilyl was eliminated. The reaction solutionwas gradually added dropwise to water for reprecipitation, therebyobtaining Ester Oligomer 1 (containing a polyacid anhydride). Themolecular weight of the oligomer was found to be 4,000. The chemicalformula of Ester Oligomer 1 is as follows:

0.05 mol of the 1,3-dichloroformyl-5-trimethylsiloxyadamantane wasdissolved in THF. To this solution were added 0.040 mol of menthanediol, and then 0.010 mol of the 1,3-dicarboxy-5-hydroxyadamantane. Themixture was stirred while keeping its temperature at room temperature,and, to this, a solution of 0.1 mol of triethylamine in THF wasgradually added dropwise. After stirring for two hours, the reactionsolution was stirred for a further two hours at room temperature. Thereaction solution was filtered, and then gradually added dropwise towater for reprecipitation. The precipitate was dissolved again in THF.By adding TBAF to this solution, trimethylsilyl was eliminated. Thereaction solution was gradually added dropwise to water forreprecipitation to obtain Ester Oligomer 2 (containing a polyacidanhydride). The molecular weight of this oligomer was found to be 3,500.Ester Oligomer 2 has the following chemical formula:

0.05 mol of the 1,3-dichloroformyl-5-trimethylsiloxyadamantane wasdissolved in THF. To this solution was added 0.050 mol of menthane diol.The mixture was stirred while keeping its temperature at roomtemperature, and, to this, a solution of 0.1 mol of triethylamine in THFwas gradually added dropwise. After stirring for two hours, the reactionsolution was stirred for a further four hours at room temperature. Thereaction solution was filtered, and then gradually added dropwise towater for reprecipitation. The precipitate was dissolved again in THF.By adding TBAF to this solution, trimethylsilyl was eliminated. Thereaction solution was gradually added dropwise to water forreprecipitation to obtain Ester Oligomer 3. The molecular weight of thisoligomer was found to be 3,000. Ester Oligomer 3 has the followingchemical formula:

[Synthesis of Comparative Polymer][Synthesis of Comparative Ester Oligomer]

0.05 mol of 1,3-diacetylchloride adamantane was dissolved in THF. Tothis solution was added 0.05 mol of menthane diol. The mixture wasstirred while keeping its temperature at room temperature, and, to this,a solution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for two hours, the reaction solution wasstirred for a further two hours at room temperature. The reactionsolution was filtered, and then gradually added dropwise to water. Theprecipitate was reprecipitated from a water-acetone solvent to obtainComparative Ester Oligomer A. This oligomer has the following chemicalformula:

[Synthesis of Dissolution-Preventive Agents]

0.1 Molar equivalent of beta-naphthol novolak was dissolved in THF. Thissolution was stirred together with a sufficient amount of di-t-butyldicarbonate in the presence of 0.1 mol of sodium hydroxide at roomtemperature for 6 hours. The reaction solution was then mixed withwater, and extracted from ethyl acetate to obtain t-butoxycarbonylatednaphthol novolak (tBocNN) with a molecular weight of 3,000. The rate ofintroduction of naphthodicarbonyl into tBocNN was 100 mol % of the totalhydroxyl group.

To tert-butyl malonate was added, in THF, an equimolar amount of sodiumhydroxide. To this mixture was added bromomethyladamantyl ketone, andthe mixture was stirred for 3 hours. The salt produced was filtered off,and the filtrate was concentrated to obtain di-tert-butyl2-((1-adamantyl)carbonylmethyl) malonate (ADTB).

1-Naphthol was condensed with glyoxylic acid in the presence of oxalicacid catalyst to obtain a novolak compound. This compound was dissolvedin dihydropyrane. To this solution was added a catalytic amount ofhydrochloric acid to obtain a pyranylated novolak compound (NV4THP).

[Preparation of Resists and Formation of Resist Patterns]

The above-synthesized resist resins and dissolution-preventive agents,and TPS-105 or NAI-105 manufactured by Midori Kagaku Co., Ltd., Japan,photo acid generator, were dissolved in cyclohexanone in accordance withthe formulations shown in Table II-8, thereby obtaining varnishes of theresists of Examples II-12 to II-16. On the other hand, a comparativevarnish was prepared by using the resist of Comparative Example II-6 andTPS-105, photo acid generator, as shown in Table II-8. TABLE II-8 AcidAdditive Generator Oligomer (%) (%) (%) Ex. II-12 Ester Oligomer 1 (99)— TPS-105 (1) Ex. II-13 Ester Oligomer 1 (79) ADTP (20) NAI-105 (1) Ex.II-14 Ester Oligomer 1 (79) NV4THP(20) NAI-105 (1) Ex. II-15 EsterOligomer 2 (99) — NAI-105 (1) Ex. II-16 Ester Oligomer 2 (99) — NAI-105(1) Comp. Ex. II-6 Comparative Ester — NAI-105 (1) Oligomer A (99)

Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper having an NA of 0.55,using as the light source, an ArF excimer laser, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by a mixture of a 2.38% aqueous solutionof tetramethylammonium hydroxide (TMH) and isopropyl alcohol toselectively dissolve and remove the exposed area, thereby formingpositive resist patterns. The sensitivities of these resists, and thedegrees of resolution of the resist patterns are shown in Table II-9.TABLE II-9 Sensitivity Resolution (mJ/cm²) (μmL/S) Remarks Ex. II-12 140.15 Pattern Configuration: good Ex. II-13 12 0.14 PatternConfiguration: good Ex. II-14 22 0.15 Pattern Configuration: good Ex.II-15 15 0.14 Pattern Configuration: good Ex. II-16 20 0.15 PatternConfiguration: good Comp. Ex. II-6 13 0.15 Pattern peeled greatly

The data shown in Table II-9 demonstrate the following: when the resistsof Examples II-12 to II-16 are used, resist patterns excellent inresolution can be formed at high sensitivities, and these resists areexcellent in transparency against light with a wavelength of 193 nm andin alkali developability; while, when the resist of Comparative ExampleII-6 is used, a resist pattern excellent in resolution cannot be formed,and the resist pattern readily peels off.

These resists were also evaluated in terms of dry-etching resistance bymeasuring their etching rates in CF₄ plasma etching. As a result, thefollowing were found: the etching rate of the resist containingpolyhydroxystyrene resin as its base resin being taken as 1.0, theetching rate of the resist of Comparative Example II-6 was 1.0, whilethose of the resists of Examples II-12 to II-16 were from 0.9 to 1.2.The resists of Examples II-12 to II-16 were thus confirmed to have highdry-etching resistance.

Examples II-17 to II-19

In THF, the following monomers, Compound II-18 and Compound II-19, weremixed with each other in a ratio of 2:8. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-17. The molecular weight of this resin was found to be 12,000.

In THF, the following monomers, Compound II-20, Compound II-21 andCompound II-22, were mixed in a ratio of 7:2:1. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-18. This resin was found to have a molecular weight of 47,000 with awide molecular weight distribution. It is assumed that a part of thepolymer is cross-linked three-dimensionally.

In THF, the following monomers, Compound II-23 and Compound II-24, weremixed with each other in a ratio of 6:4. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-19. The molecular weight of this resin was found to be 17,000.

One part by weight of TPS-105 manufactured by Midori Kagaku Co., Ltd.,Japan was added as a photo acid generator to each one of theabove-synthesized polymers of Examples of II-17 to II-19. These mixtureswere respectively dissolved in cyclohexanone, and the solutions werefiltered to obtain varnishes of the resists of Examples II-17 to II-19.

Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.54,using an ArF excimer laser as the light source, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by a 2.38% aqueous solution oftetramethylammonium hydroxide (TMH) to selectively dissolve and removethe exposed area, thereby forming positive resist patterns. Thesensitivities of these resists, and the degrees of resolution of theresist patterns are shown in Table II-10. TABLE II-10 SensitivityResolution Resist (mJ/cm²) (μml/S) Ex. II-17 13 0.15 Ex. II-18 12 0.14Ex. II-19 12 0.14

The data shown in Table II-10 demonstrate the following: when theresists of Examples II-17 to II-19 are used, resist patterns excellentin resolution can be formed at high sensitivities, and these resists areexcellent both in transparency against light with a wavelength of 193 nmand alkali developability.

These resists were also evaluated in terms of dry-etching resistance bymeasuring their etching rates in CF₄plasma etching. As a result, thefollowing were found: the etching rate of the resist containing anovolak resin as its base being taken as 1.0, the etching rate of theresist of Comparative Example II-6 was 1.2, while those of the resistsof Examples II-17 to II-19 were from 0.9 to 1.0. The resists of ExamplesII-17 to II-19 were thus confirmed to have high dry-etching resistance.

Examples II-20 and II-21

The following monomer, Compound II-26, and Compound II-19 were mixedwith each other in THF in a ratio of 4:6. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-20. The molecular weight of this resin was found to be 10,000.

Compound II-20, and the following monomer, Compound II-27, were mixedwith each other in THF in a ratio of 6:4. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of Example II-21. The molecular weight of this resin was found to be 12,000.

Examples II-22 and II-23

The following monomer, Compound II-28, and Compound II-19 were mixedwith each other in THF in a ratio of 4:6. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a polymer of ExampleII-22. The molecular weight of this polymer was found to be 6,000.

The following monomer, Compound II-29, and Compound II-20 were mixedwith each other in THF in a ratio of 2:8. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a polymer of ExampleII-23. The molecular weight of this polymer was found to be 7,500.

One part by weight of TPS-105 manufactured by Midori Kagaku Co., Ltd.,Japan was added, as a photo acid generator, to each one of theabove-synthesized resist resins of Examples of II-20 to II-23. Thesemixtures were respectively dissolved in cyclohexanone, and the solutionswere filtered to obtain varnishes of the resists of Examples II-20 toII-23.

Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using an ArF excimer laser as the light source, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by an aqueous solution oftetramethylammonium hydroxide (TMH) to selectively dissolve and removethe exposed area, thereby forming positive resist patterns. Thesensitivities of these resist resins and the degrees of resolution ofthe resist patterns are shown in Table II-11. TABLE II-11 SensitivityResolution Resist (mJ/cm²) (μmL/S) Ex. II-20 10 0.14 Ex. II-21 11 0.14Ex. II-22 15 0.14 Ex. II-23 13 0.14

The resists of Examples II-20 to II-23 were also evaluated in terms ofdry-etching resistance by measuring their etching rates in CF₄ plasmaetching. As a result, it was confirmed that their dry-etching resistancewas 0.8 to 1.0 time that of novolak resin.

Examples II-24 and II-25 and Comparative Example II-7

The following monomers, Compound II-30 and Compound II-31, were mixedwith each other in THF in a ratio of 4:6. To this mixture was added 10mol % of AIBN, and copolymerization was conducted at 60° C. for 40hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-24. The molecular weight of this resin was found to be 6,000.

The following monomers, Compound II-32 and Compound II-33, and maleicanhydride were mixed in THF in a ratio of 3.5:3:3.5. To this mixture wasadded 10 mol % of AIBN, and copolymerization was conducted at 60° C. for40 hours. The reaction solution was added dropwise to hexane. Theprecipitate was filtered off, and dried to obtain a resin of ExampleII-21. The molecular weight of this resin was found to be 5,500.

As Comparative Example II-7, Compound II-32,2-acryloyloxy-7-hydroxy-methyltricyclodecane and maleic anhydride weremixed in THF in a ratio of 3.5:3:3.5. To this mixture was added 10 mol %of AIBN, and copolymerization was conducted at 60° C. for 40 hours. Thereaction solution was added dropwise to hexane. The precipitate wasfiltered off, and dried to obtain a resin of Comparative Example II-7.The molecular weight of this resin was found to be 9,000.

One part by weight of TPS-105 manufactured by Midori Kagaku Co., Ltd.,Japan was added, as a photo acid generator, to each one of theabove-synthesized resist resins of Examples of II-24 and II-25, andComparative Example II-7. These mixtures were respectively dissolved incyclohexanone, and the solutions were filtered to obtain varnishes ofthe resists of Examples II-24 and II-25 and of Comparative Example II-7.

Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicone wafers to form resists films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using an ArF excimer laser as the light source, thereby conductingpattern-wise exposure. Thereafter, the resist films were baked at 110°C. for 2 minutes, and developed by an aqueous solution oftetramethylammonium hydroxide (TMH) to selectively dissolve and removethe exposed area, thereby forming a positive resist pattern. Thesensitivities of the resist resins and the degrees of resolution of theresist patterns are shown in Table II-12. TABLE II-12 SensitivityResolution (mJ/cm²) (μmL/S) Remarks Ex. II-24 12 0.14 PatternConfigulation: good Ex. II-25 17 0.13 Pattern Configulation: good Comp.Ex. II-7 55 0.5 Scummy

The data shown in Table II-12 demonstrate that remarkably good effectsare obtained when the resin structure of the present invention iscombined with maleic anhydride. The resists of Examples II-24 and II-25were also evaluated in terms of dry-etching resistance by measuringtheir etching rates inCF₄ plasma etching. As a result, it was confirmedthat their dry-etching resistance was 0.8 to 1.0 time that of novolakresin. Examples III-1 to III-9 and Comparative Examples III-1 to III-4<Synthesis of Starting Compounds (Adamantane Compounds (Monomers) Having>C═O)>

[Synthesis of Compound (III-A) and Compound (III-B)]

One mol of 2-adamantyl ketone was stirred in an acetic acid-aceticanhydride solution of CrO₃, oxidizing agent, with heating. Aftercarrying out the reaction for 8 hours, the reaction solution wasneutralized to obtain a mixture of polydroxylated compounds of adamantylketone. This mixture was partitioned by high performance liquidchromatography to obtain 1-hydroxy-4-adamantanone (Compound (III-A)),and 1,3-dihydroxy-6-adamantanone (Compound (III-B)).

[Synthesis of Compound (III-C)

In the same manner as in the synthesis of Compound (III-A) and (III-B),1,3-dicarboxyadamantane was oxidized, and partition was conducted toobtain 1,3-dicarboxy-6-adamantanone (Compound (III-C)).

[Synthesis of Compound (III-D)]

Compound (III-C) was dissolved in THF, and reacted with an excessiveamount of thionyl chloride for 4 hours under reflux. The excessivethionyl chloride and solvent were distilled off to obtain an acidchloride compound of Compound (III-C) (Compound (III-D)).

[Synthesis of Compound (III-E)]

Compound (III-A) was dissolved in THF, and stirred together with anequimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The salt precipitated was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofCompound (III-A) (Compound (III-E)).

The ¹HNMR chart of this compound is shown in FIG. 4.

[Synthesis of Compound (III-F)]

Compound (III-E) and an equimolar amount of2,2′-dimethyl-1,3-dioxane-4,6-dione were stirred in pyridine at roomtemperature for one week. The reaction product was added dropwise towater to obtain 1-acryloyloxylated4-(5-adamatylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione (Compound(III-F)). The ¹HNMR chart of this compound is shown in FIG. 5.

[Synthesis of Compound (III-G)]

Dihydropyrane was added to methacrylic acid by the use of an acidcatalyst to obtain tetrahydropyranyl methacrylate (Compound (III-G)).

[Synthesis of Compound (III-H)]

1-Adamantanol and acrylic acid chloride were subjected to desaltingreaction by the use of a basic catalyst to obtain adamantyl acrylate(Compound (III-H)).

It is noted that methacrylic acid, menthane diol and 1,3-dicarboxyladamantane were reagents manufactured by Aldrich Chemical Company, Inc.,and used as they were.

[Synthesis of Compound (III-I)]

2-Methyl-2-adamantanol was dissolved in methylene chloride, and thesolution was stirred together with an equimolar amount of acrylic acidchloride. To this mixture was added dropwise an excessive amount oftriethylamine at room temperature, and the mixture was stirred for 3hours. The salt precipitated was filtered off, and the filtrate wasconcentrated to obtain an acrylic ester of 2-methyl-2-adamantanol(Compound (III-I)).

[Synthesis of Compound (III-J)]

Hydroxypinanone was dissolved in THF, and the solution was stirredtogether with an equimolar amount of acrylic acid chloride. To thismixture was added dropwise an excessive amount of triethylamine at roomtemperature, and the mixture was stirred for 3 hours. The saltprecipitated was filtered off, and the filtrate was concentrated toobtain an acrylic ester of hydroxypinanone (Comparative Monomer J).

<Synthesis of Resins>

0.6 mol of Compound (III-E) and 0.4 mol of Compound (III-G) were mixedwith 200 g of THF. Subsequently, 2 g of AIBN was added to this mixture,and the resulting mixture was heated at 60° C. for 36 hours. Thereaction solution was added dropwise to hexane to obtain Copolymer III-1having an average molecular weight of approximately 7,000. Thestructural formula of Copolymer III-1 is as follows:

0.6 mol of Compound (III-F) and 0.4 mol of Compound (III-G) were mixedwith 200 g of THF. Subsequently, 2 g of AIBN was added to this mixture,and the resulting mixture was heated at 60° C. for 36 hours. Thereaction solution was added dropwise to hexane to obtain Copolymer III-2having an average molecular weight of approximately 8,000. Thestructural formula of Copolymer III-2 is as follows:

0.6 mol of Compound (III-E) and 0.4 mol of Compound (III-I) were mixedwith 200 g of THF. Subsequently, 2 g of AIBN was added to this mixture,and the resulting mixture was heated at 60° C. for 36 hours. Thereaction solution was added dropwise to hexane to obtain Copolymer III-3having an average molecular weight of approximately 5,000. Thestructural formula of Copolymer III-3 is as follows:

0.04 mol of Compound (III-B) was dissolved in THF. To this solution wereadded 0.05 mol of Compound (III-D), and then 0.010 mol of Compound(III-C). The mixture was stirred while keeping its temperature at roomtemperature, and, to this, a solution of 0.1 mol of triethylamine in THFwas gradually added dropwise. After stirring for 2 hours, the mixturewas stirred at room temperature for a further 2 hours, and the reactionsolution was filtered. The filtrate was gradually added dropwise towater, and the precipitate was reprecipitated to obtain Ester OligomerIII-4 (containing a polyacid anhydride). The average molecular weight ofthis oligomer was found to be 4,000. The structural formula of EsterOligomer III-4 is as follows:

0.05 mol of Compound (III-D) was dissolved in THF. To this solution wereadded 0.040 mol of menthane diol, and then 0.010 mol of Compound(III-C). The mixture was stirred while keeping its temperature at roomtemperature, and, to this, a solution of 0.1 mol of triethylamine in THFwas gradually added dropwise. After stirring for 2 hours, the mixturewas stirred at room temperature for a further 2 hours, and the reactionsolution was filtered. The filtrate was gradually added dropwise towater, and the precipitate was reprecipitated to obtain Ester OligomerIII-5 (containing a polyacid anhydride). The average molecular weight ofthis oligomer was found to be 3,500. The structural formula of EsterOligomer III-5 is as follows:

0.05 mol of Compound (III-D) was dissolved in THF. To this solution wasadded 0.050 mol of menthane diol. The mixture was stirred while keepingits temperature at room temperature, and, to this, a solution of 0.1 molof triethylamine in THF was gradually added dropwise. After stirring for2 hours, the mixture was stirred at room temperature for a further 4hours, and the reaction solution was filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated to obtain Ester Oligomer III-6. The average molecularweight of this oligomer was found to be 3,000. The structural formula ofEster Oligomer III-6 is as follows:

<Synthesis of Comparative Acrylate Polymers>

0.6 mol of the adamatyl acrylate (Compound (III-H)) and 0.4 mol of thetetrahydropyrany methacrylate (Compound (III-G)) were reacted with eachother in THF for 40 hours by the use of AIBN(10 mol %) as an initiator.The reaction solution was added dropwise to hexane to obtain ComparativeAcrylate Polymer III-A. The structural formula of this polymer is asfollows:

0.6 mol of Compound (III-J) and 0.4 mol of Compound (III-G) were mixedwith 200 g of THF. Subsequently, 2 g of AIBN was added to this mixture,and the resulting mixture was heated at 60° C. for 36 hours. Thereaction solution was added dropwise to hexane to obtain ComparativeAcrylate Polymer III-B having an average molecular weight ofapproximately 10,000. The structural formula of this polymer is asfollows:

0.5 mol of Compound (III-E), 0.4 mol of Compound (III-G) and 0.1 mol ofmethacrylic acid were mixed with 200 g of THF. Subsequently, 2 g of AIBNwas added to this mixture, and the resulting mixture was heated at 60°C. for 36 hours. The reaction solution was added dropwise to hexane toobtain Comparative Acrylate Polymer III-C having an average molecularweight of approximately 8,000. The structural formula of this polymer isas follows:

<Synthesis of Comparative Ester Polymer>

0.05 mol of adamantandicarbonyl chloride was dissolved in THF, and tothis solution was added 0.05 mol of menthane diol. The mixture wasstirred while keeping its temperature at room temperature, and, to this,a solution of 0.1 mol of trimethylamine in THF was gradually addeddropwise. After stirring for two hours, the reaction solution wasstirred for a further 2 hours, and then filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated from a water-acetone solvent to obtain Comparative EsterOligomer III-D. The structural formula of this oligomer is as follows:

<Synthesis of Dissolution-Preventive Agents>

Beta-naphthol novolak in an amount of 0.1 mol in terms of naphthol wasdissolved in THF. This solution was stirred together with a sufficientamount of di-t-butyl dicarbonate in the presence of 0.1 mol of sodiumhydroxide at room temperature for 6 hours. The reaction solution wasmixed with water, and extracted from ethyl acetate to obtaint-butoxycarbonylated naphthol novolak (tBocNN) having a molecular weightof 3,000. The rate of introduction of t-butoxycarbonyl into the tBocNNwas 100 mol % of the total hydroxyl group.

To tert-butyl malonate was added, in THF, an equimolar amount of sodiumhydroxide. To this mixture was added bromomethyl amadantyl ketone, andthe mixture was stirred for 3 hours. The salt precipitated was filteredoff, and the filtrate was concentrated to obtain di-tert-butyl2-((1-amadantyl)carbonyl-methyl)malonate (ADTB).

1-Naphthol was condensed with glyoxylic acid in the presence of oxalicacid catalyst to obtain a novolak compound. This compound was dissolvedin dihydropyrane. To this solution was added a catalytic amount ofhydrochloric acid to obtain a pyranylated novolak compound (NV4THP).

<Preparation of Resists & Formation of Resist Patterns>

The above-synthesized polymer compounds and dissolution-preventiveagents, and TPS-105 or NAI-105 manufactured by Midori Kagaku Co., Ltd.,Japan, photo acid generator, were dissolved in cyclohexanone (polyestertype) or PGMEA (acrylic type) in accordance with the formulations shownin Tables III-1 and III-2 to obtain varnishes of the resists of ExamplesIII-1 to III-9. TABLE III-1 Acid Polymer or Oligomer Generator (%)Additive (%) (%) Ex. III-1 Copolymer 1 (99) — TPS-105 (1) Ex. III-2Copolymer 1 (79) t-BocNN (20) TPS-105 (1) Ex. III-3 Copolymer 2 (99) —TPS-105 (1) Ex. III-4 Copolymer 3 (99) — TPS-105 (1) Ex. III-5 EsterOligomer 4 (99) — TPS-105 (1) Ex. III-6 Ester Oligomer 4 (79) ADTB (20)NAI-105 (1) Ex. III-7 Ester Oligomer 4 (79) NV4THP (20) NAI-105 (1) Ex.III-8 Ester Oligomer 5 (99) — NAI-105 (1) Ex. III-9 Ester Oligomer 6(99) — TPS-105 (1)

On the other hand, comparative varnishes III-1 to III-4 were prepared byusing the comparative polymers, and TPS-105, photo acid generator, asshown in Table III-2. TABLE III-2 Acid Polymer or Oligomer Generator (%)Additive (%) (%) Comp. Ex. III-1 Comparative Acryl — TPS-105 (1) PolymerA (99) Comp. Ex. III-2 Comparative Acryl — TPS-105 (1) Polymer B (99)Comp. Ex. III-3 Comparative Acryl — TPS-105 (1) Polymer C (99) Comp. Ex.III-4 Comparative Acryl — TPS-105 (1) Polymer D (99)

Subsequently, these varnishes of the resists were respectivelyspin-coated onto silicon wafers to form resist films, each having athickness of 0.3 micrometers. These resists films were respectivelyexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using as the light source an ArF excimer laser, thereby conductingpattern-wise exposure. Thereafter, these resist films were baked at 110°C. for 2 minutes, and then developed by a mixture of a 2.38% aqueoussolution of tetramethylammonium hydroxide (TMAH), MAH and isopropylalcohol. The exposed area was thus selectively dissolved and removed toform positive resist patterns. The sensitivities of the resist resins,and the degrees of resolution of the resist patterns are shown in TableIII-3. TABLE III-3 Sensitivity Resolution (mJ/cm²) (μmL/S) Remarks Ex.III-1 5 0.15 Good Ex. III-2 15 0.15 Good Ex. III-3 10 0.15 Good Ex.III-4 7 0.14 Good Ex. III-5 14 0.15 Good Ex. III-6 12 0.14 Good Ex.III-7 22 0.15 Good Ex. III-8 15 0.14 Good Ex. III-9 20 0.15 Good Comp.Ex. III-1 22 0.35 Impossible to form fine pattern Comp. Ex. III-2 100.19 Pattern peeled greatly Comp. Ex. III-3 7 0.17 Pattern peeledgreatly, used thin developer Comp. Ex. III-4 3 0.15 Pattern peeledgreatly

The date shown in Table III-3 demonstrate the following: when theresists of Examples III-1 to III-9 are used, resist patterns excellentin resolution can be formed at high sensitivities, and these resists areexcellent in both transparency against light with a wavelength of 193 nmand alkali developability; while, when the resists of Comparative III-1to III-3 are used, resist patterns excellent in resolution cannot beformed, and the resist films readily peel off.

In addition, these resists were evaluated in terms of dry-etchingresistance by measuring their etching rates in CF₄ plasma etching. As aresult, it was found the following: the etching rate of the resistcontaining as its base resin polyhydroxystyrene resin being taken as1.0, the etching rates of the resists of Comparative Examples III-1 andIII-4 are from 1.0 to 1.3 (moderate), and those of the resists ofComparative Examples III-2 and III-3 are approximately 1.4 to 1.6(poor); while the etching rates of the resists of Examples III-1 toIII-9 are from 0.9 to 1.2. The resists of Examples III-1 to III-9 arethus confirmed to have high dry-etching resistance.

Examples III-10 to III-18 and Comparative Examples III-5 to III-9

<Synthesis of Starting Compounds (Adamantane Compounds (Monomers) HavingLactonyl Group)>

[Synthesis of Compound (III-a) and Compound (III-b)]

One mol of 2-adamantyl ketone was stirred in an acetic acid-aceticanhydride solution of CrO₃, oxidizing agent, with heating. Aftercarrying out the reaction for 8 hours, the reaction solution wasneutralized to obtain a mixture of polyhydroxylated compounds ofadamantyl ketone. This mixture was partitioned by high performanceliquid chromatography to obtain 1-hydroxy-4-adamantanone (Compound(III-a)) and 1,3-dihydroxy-6-adamantanone (Compound (III-b)).

[Synthesis of Compound (III-c)]

Similarly, 1,3-dicarboxyadamantane was oxidized, and partition wasconducted to obtain 1,3-dicarboxy-6-adamantanone, Compound (III-c).

[Synthesis of Compound (III-d)]

Compound (III-c) was dissolved in THF, and reacted with an excessiveamount of thionyl chloride under reflux for 4 hours. The excessivethionyl chloride and solvent were distilled off to obtain an acidchloride compound of Compound (III-c) (Compound (III-d)).

[Synthesis of Compound (III-a′)]

Compound (III-a) was dissolved in dichloromethane. To this solution wasadded methachloroperbenzoic acid, and the mixture was stirred at roomtemperature for 1 hour. The reaction solution was then treated withdiazomethane to obtain a lactone (Compound (III-a′)).

[Synthesis of Compound (III-b′)]

Compound (III-b) was dissolved in dichloromethane. To this solution wasadded methachloroperbenzoic acid, and the mixture was stirred at roomtemperature for 1 hour. The reaction solution was then treated withdiazomethane to obtain a lactone (Compound (III-b′)).

[Synthesis of Compound (III-c′)]

Similarly, 1,3-dicarboxyadamantane was oxidized, and partition wasconducted to obtain a lactone (Compound (III-c′)).

[Synthesis of Compound (III-d′)]

Compound (III-c′) was dissolved in THF, and reacted with an excessiveamount of thionyl chloride under reflux for 4 hours. The excessivethionyl chloride and solvent were distilled off to obtain an acidchloride compound of Compound (III-c′) (Compound (III-d′)).

[Synthesis of Compound (III-e)]

Compound (III-a′) was dissolved in THF, and stirred together with anequimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The precipitated salt was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofCompound (III-a′) (Compound III-e, R in the general formula (3) beingacryloyl group).

[Synthesis of Compound (III-f)]

Compound (III-b′) was dissolved in THF, and stirred with an equimolaramount of acrylic acid chloride. To this mixture was added dropwise anexcessive amount of triethylamine at room temperature, and the mixturewas stirred for 3 hours. The precipitated salt was filtered off, and thefiltrate was concentrated to obtain an acrylic ester of Compound(III-b′) (Compound III-f, R in the general formula (4) being acryloylgroup).

[Synthesis of Compound (III-g)]

Dihydropyrane was added to methacrylic acid by the use of an acidcatalyst to obtain tetrahydropyranyl methacrylate (Compound (III-g)).

[Synthesis of Compound (III-h)]

1-Adamantanol and acrylic acid chloride were subjected to desaltingreaction by using a basic catalyst to obtain adamantyl acrylate(Compound (III-h)).

Methacrylic acid, menthane diol and 1,3-dicarboxyl adamantane arereagents manufactured by Aldrich Chemical Company, Inc., and were usedas they were.

[Synthesis of Compound (III-i)]

2-Methyl-2-adamantanol was dissolved in methylene chloride, and stirredtogether with an equimolar amount of acrylic acid chloride. To thismixture was added dropwise an excessive amount of triethylamine at roomtemperature, and the mixture was stirred for 3 hours. The precipitatedsalt was filtered off, and the filtrate was concentrated to obtain anacrylic ester of 2-methyl-2-adamantanol (Compound (III-i)).

[Synthesis of Compound (III-j))

Hydroxypinanone was dissolved in THF, and stirred together with anequimolar amount of acrylic acid chloride. To this mixture was addeddropwise an excessive amount of triethylamine at room temperature, andthe mixture was stirred for 3 hours. The precipitated salt was filteredoff, and the filtrate was concentrated to obtain an acrylic ester ofhydroxypinanone (Comparative Compound (III-j)).

<Synthesis of Resins>

0.6 mol of Compound (III-e) and 0.4 mol of Compound (III-g) were mixedwith 200 g of THF. To this mixture was then added 2 g of AIBN, and themixture was heated at 60° C. for 36 hours. The reaction solution wasadded dropwise to hexane to obtain Copolymer III-7 having an averagemolecular weight of approximately 7,000. The structural formula of thiscopolymer is as follows:

0.6 mol of Compound (III-f) and 0.4 mol of Compound (III-g) were mixedwith 200 g of THF. To this mixture was then added 2 g of AIBN, and themixture was heated at 60° C. for 36 hours. The reaction solution wasadded dropwise to hexane to obtain Copolymer III-8 having an averagemolecular weight of approximately 8,000. The structural formula of thiscopolymer is as follows:

0.6 mol of Compound (III-e) and 0.4 mol of Compound (III-i) were mixedwith 200 g of THF. To this mixture was then added 2 g of AIBN, and themixture was heated at 60° C. for 36 hours. The reaction solution wasadded dropwise to hexane to obtain Copolymer III-9 having an averagemolecular weight of approximately 5,000. The structural formula of thiscopolymer is as follows:

0.05 mol of Compound (III-b′) was dissolved in THF. To this solutionwere added 0.040 mol of Compound (III-d), and then 0.010 mol of Compound(III-c). The mixture was stirred while maintaining its temperature atroom temperature, and, to this, a solution of 0.1 mol of triethylaminein THF was gradually added dropwise. After stirring for 2 hours, themixture was stirred for a further 2 hours at room temperature, and thenfiltered. The filtrate was gradually added dropwise to water, and theprecipitate was reprecipitated to obtain Ester Oligomer III-10(containing a polyacid anhydride). The average molecular weight of thisoligomer was found to be 4,000. The structural formula of this oligomeris as follows:

0.05 mol of Compound (III-d′) was dissolved in THF. To this solutionwere added 0.040 mol of menthane diol, and then 0.010 mol of Compound(III-c). The mixture was stirred while maintaining its temperature atroom temperature, and, to this, a solution of 0.1 mol of triethylaminein THF was gradually added dropwise. After stirring for 2 hours, themixture was stirred for a further 2 hours at room temperature, and thenfiltered. The filtrate was gradually added dropwise to water, and theprecipitate was reprecipitated to obtain Ester Oligomer III-11(containing a polyacid anhydride). The average molecular weight of thisoligomer was found to be 3,500. The structural formula of this oligomeris as follows:

0.05 mol of Compound (III-d′) was dissolved in THF. To this solution wasadded 0.050 mol of menthane diol. The mixture was stirred whilemaintaining its temperature at room temperature, and, to this, asolution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for 2 hours, the mixture was stirred for afurther 4 hours at room temperature, and then filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated to obtain Ester Oligomer III-12. The average molecularweight of this oligomer was found to be 3,000. The structural formula ofthis oligomer is as follows:

[Synthesis of Comparative Acrylate Polymer]

0.6 mol of the adamantyl acrylate (Compound (III-h)) and 0.4 mol of thetetrahydropyranyl methacrylate (Compound (III-g)) were reacted with eachother in THF for 40 hours by using AIBN (10 mol %) as an initiator. Thereaction solution was added dropwise to hexane to obtain ComparativeAcrylate Polymer III-E. The structural formula of this polymer is asfollows:

[Synthesis of Comparative Ester Oligomer]

0.05 mol of adamatandicarbonyl chloride was dissolved in THF, and tothis solution was added 0.05 mol of menthane diol. The mixture wasstirred while maintaining its temperature at room temperature, and, tothis, a solution of 0.1 mol of triethylamine in THF was gradually addeddropwise. After stirring for two hours, the reaction solution wasstirred for a further 2 hours, and then filtered. The filtrate wasgradually added dropwise to water, and the precipitate wasreprecipitated from a water-acetone solvent to obtain Comparative EsterOligomer III-F. The structural formula of this oligomer is as follows:

[Comparative Acrylate Polymer]

Comparative Acrylate Polymers III-G, III-H and III-I described inJapanese Patent Laid-Open Publication No.3169/1998, having the followinggeneral formulas were prepared.

[Preparation of Resists and Formation of Resist Patterns]

The above-synthesized polymer compounds and dissolution-preventiveagents, and TPS-105 or NAI-105 manufactured by Midori Kagaku Co., Ltd.,Japan, photo acid generator, were dissolved in cyclohexanone (polyestertype) or PGMEA (acrylic ester type) in accordance with the formulationsshown in Table III-4 to obtain varnishes of the resists of ExamplesIII-10 to III-18. TABLE III-4 Acid Polymer or Oligomer Generator (%)Additive (%) (%) Ex. III-10 Copolymer 7 (99) — TPS-105 (1) Ex. III-11Copolymer 7 (79) t-BocNN (20) TPS-105 (1) Ex. III-12 Copolymer 8 (99) —TPS-105 (1) Ex. III-13 Copolymer 9 (99) — TPS-105 (1) Ex. III-14 EsterOligomer10 (99) — TPS-105 (1) Ex. III-15 Ester Oligomer 10(79) ADTB (20)NAI-105 (1) Ex. III-16 Ester Oligomer10 (79) NV4THP (20) NAI-105 (1) Ex.III-17 Ester Oligomer11 (99) — NAI-105 (1) Ex. III-18 Ester Oligomer12(99) — TPS-105 (1)

On the other hand, varnishes of the resists of Comparative ExamplesIII-5 to III-9 were prepared by using the comparative polymers, and, asa photo acid generator, TPS-105 as shown in Table III-5. TABLE III-5Acid Polymer or Oligomer Generator (%) Additive (%) (%) Comp. Ex. III-5Comparative Acryl — TPS-105 (1) Polymer E (99) Comp. Ex. III-6Comparative Acryl — TPS-105 (1) Polymer F (99) Comp. Ex. III-7Comparative Acryl — TPS-105 (1) Polymer G (99) Comp. Ex. III-8Comparative Acryl — TPS-105 (1) Polymer H (99) Comp. Ex. III-9Comparative Acryl — TPS-105 (1) Polymer I (99)

Subsequently, the varnishes of these resists were respectivelyspin-coated onto silicon wafers to form resist films, each having athickness of 0.3 micrometers. The surfaces of these resist films wereexposed to light of 193 nm emitted by a stepper with an NA of 0.55,using as the light source an ArF excimer laser, thereby conductingpattern-wise exposure. The resist films were then baked at 110° C. for 2minutes, and developed by a mixture of a 2.38% aqueous solution oftetramethyl-ammonium hydroxide (TMAH), MAH and isopropyl alcohol. Theexposed area was thus selectively dissolved and removed to form positiveresist patterns. The sensitivities of the resists, and the degrees ofresolution of the resist patterns are as shown in Table III-6. TABLEIII-6 Sensitivity Resolution (mJ/cm²) (μmL/S) Remarks Ex. III-10 5 0.15Good Ex. III-11 15 0.15 Good Ex. III-12 10 0.15 Good Ex. III-13 7 0.14Good Ex. III-14 14 0.15 Good Ex. III-15 12 0.14 Good Ex. III-16 22 0.15Good Ex. III-17 15 0.14 Good Ex. III-18 20 0.15 Good Comp. Ex. III-5 220.35 Impossible to form fine pattern Comp. Ex. III-6 10 0.19 Patternpeeled greatly Comp. Ex. III-7 13 0.35 Impossible to form fine patternComp. Ex. III-8 20 0.35 Impossible to form fine pattern Comp. Ex. III-913 0.20 Pattern peeled greatly

The date shown in Table III-6 demonstrate the following: when theresists of Examples of III-10 to III-18 are used, resist patternsexcellent in resolution are formed at high sensitivities, and theresists are excellent in both transparency against light of 193 nm andalkali developability; while, when the resists of Comparative ExamplesIII-5 to III-9 are used, resist patterns excellent in resolution cannotbe formed, and the resist films readily peel off.

In addition, these resists were evaluated in terms of dry-etchingresistance by measuring their etching rates in CF₄ plasma etching. As aresult, the following were found: the etching rate of the resistcontaining as its base resin polyhydroxystyrene resin being taken as1.0, the etching rates of the resists of Comparative Examples III-5 andIII-6 were from 1.0 to 1.3 (moderate), and those of the resists ofComparative Examples III-7, III-8 and III-9 were approximately 1.4 to1.6 (poor); while the etching rates of the resists of Examples III-10 toIII-18 were from 0.9 to 1.2. The resists of Examples III-10 to III-18were thus confirmed to have high dry-etching resistance.

1-29. (Canceled).
 30. A resin comprising a polymer compound produced byhomopolymerizing at least one monomer selected from monomers representedby the general formulas (I-1) and (I-2):

wherein R is acryloyl or methacryloyl group, R₁₁ and R₁₂ are hydrogenatom or a monovalent alkyl group, with proviso that at least one of R₁₁and R₁₂ is monovalent alkyl group, and R₁₃ is oh group, ═O group, COOHgroup or COOR₁₄ group, wherein R₁₄ is a monovalent organic group, or bycopolymerizing the monomer(s) and any other vinyl monomer:
 31. The resinaccording to claim 30, wherein the monovalent alkyl group is selectedfrom the group consisting of methyl, ethyl, propyl, and iso-propylgroups.
 32. The resin according to claim 30, wherein both R₁₁ and R₁₂are monovalent alkyl groups.
 33. The resin according to claim 32,wherein the monovalent alkyl group is selected from the group consistingof methyl, ethyl, propyl, and iso-propyl groups.
 34. The resin accordingto claim 30, wherein R₁₃ is ═O group.
 35. The resin according to claim30, wherein at least one of R₁₁ and R₁₂ contained in the resist resin isselected from the group consisting of C₂H₅ group, C₃H₇ group and C₄H₉group.
 36. The resin according to claim 30, wherein R₁₃ is combined witha tertiary carbon atom.